drilling mud pump calculations made in china

Rig pump output, normally in volume per stroke, of mud pumps on the rig is  one of important figures that we really need to know because we will use pump out put figures to calculate many parameters such as bottom up strokes,  wash out depth, tracking drilling fluid, etc. In this post, you will learn how to calculate pump out put for triplex pump and duplex pump in bothOilfield and Metric Unit.

Bourgoyne, A.J.T., Chenevert , M.E. & Millheim, K.K., 1986. SPE Textbook Series, Volume 2: Applied Drilling Engineering, Society of Petroleum Engineers.

Drilling fluids are a vital part of drilling operations. It controls wellbore pressure, lubricates and cools the drill bit, carries the drill cuttings, and other essential functions. To fulfill these tasks, carefully chosen additives are incorporated into the mud to control its properties. It is the mud engineer"s responsibility to ensure that any new mud that is produced and added meets the required specifications.

In the past, mud engineers relied on paper forms or Excel® spreadsheets to record mud properties, product usage, and inventory on a daily basis. This approach meant that engineers encountered a variety of issues, such as disorganization of numerous daily reports and difficulty with generating end-of-well recaps.

MUDPRO is a mud reporting software that complies with API specifications for field use. With an advanced database, this innovative, all-inclusive model significantly improves drilling fluid data gathering, sharing and management.

MUDPRO is designed for both mud engineers at rig sites and engineering managers. A mud engineer will use the software to record mud data and generate daily reports whereas a manager can use MUDPRO to review and manage data, make an end-of-well recap and compare multiple wells.

Our advanced version, MUDPRO+, includes enhanced mud volume tracking and concentration calculations, which are more accurate and effective in handling a variety of mud volume transitions.

Up and coming! Our all new next generation of MUDPRO is being developed for its release this year. An all-new dazzling visualization, added machine learning, an at-a-glance dashboard and much more. We are commencing MUDPRO’s advancement to bring you a better, improved daily mud reporting software to meet your daily needs. Stay tuned for its release date and experience the next generation of MUDPRO for yourself.

Investigation of propagation characteristics of a pressure wave is of great significance to the solution of the transient pressure problem caused by unsteady operations during management pressure drilling operations. With consideration of the important factors such as virtual mass force, drag force, angular frequency, gas influx rate, pressure, temperature, and well depth, a united wave velocity model has been proposed based on pressure gradient equations in drilling operations, gas-liquid two-fluid model, the gas-drilling mud equations of state, and small perturbation theory. Solved by adopting the Runge-Kutta method, calculation results indicate that the wave velocity and void fraction have different values with respect to well depth. In the annulus, the drop of pressure causes an increase in void fraction along the flow direction. The void fraction increases first slightly and then sharply; correspondinglythe wave velocity first gradually decreases and then slightly increases. In general, the wave velocity tends to increase with the increase in back pressure and the decrease of gas influx rate and angular frequency, significantly in low range. Taking the virtual mass force into account, the dispersion characteristic of the pressure wave weakens obviously, especially at the position close to the wellhead.

One of the future trends of the petroleum industry is the exploration and development of high pressure, low permeability reservoirs [1]. Drilling-related issues such as excessive mud cost, wellbore ballooning/breathing, kick-detection limitations, difficulty in avoiding gross overbalance conditions, differentially stuck pipe, and resulting well-control issues together contribute to the application of managed pressure drilling (MPD) technology [2]. MPD technology has the ability to quickly react to the expected drilling problems and formations pressures uncertainties, reduce nonproductive time and mitigating drilling hazards, and offer a considerable amount of tangible benefits while drilling in extremely narrow fracture/pore pressure windows [3]. It allows drilling operations to proceed where conventional drilling is easy to cause formation damage or considered uneconomical,

of high risk, or even impossible [4]. Although drilling operators try to avoid the risk of influxes, occasionally there are influxes for various reasons. Gas influx occurs whenever the pressure of a gas-bearing formation exceeds the pressure at the bottom of a wellbore. Since the subsequent intrusion of gas displaces drilling mud, it decreases the pressure in the wellbore and makes gas enter even faster [5, 6]. If it is not counteracted in time, the unstable effect can escalate into a blowout creating severe financial losses, environmental contamination, and potential loss of human lives. The basic principle of MPD well control is to keep the bottomhole pressure (BHP) as constant as possible at a value that is at least equal to the formation pressure [7]. MPD is a class of techniques that allow precise management of BHP under both static and dynamic conditions through a combination of controlling the flow rate, mud density, and back pressure (or wellhead pressure) on the fluid returns (choke manifold) of

During the managed pressure drilling process, all the unsteady operations such as adjustment of choke, wellhead backpressure controls [11], tripping in/out [12], shutting-in [13], and mud pump rate changes [14] will cause generation and propagation of pressure waves, which would threaten the whole drilling system from the wellhead facilities to the bottomhole drilling equipment and the formation [15]. In the analysis of an influx well and formulation of well control scheme, the dynamic effects of these operations, appeared as pressure fluctuations, should be accounted for [16]. As a basic parameter of pressure fluctuation, the pressure wave velocity has close relevance with the determination of transient pressure and safe operating parameters for well control. However, the gas influx is more troublesome for the higher compressibility and lower density of influx gas than the single phase drilling mud [17]. The works of Bacon et al. [18] had demonstrated that compressibility effects of a gas influx can be significant during an applied-back-pressure, dynamic, MPD well control response and can impact the well control process. Hence, this paper considered the propagation behavior of pressure wave in gas-drilling mud two-phase flow in the annulus to provide reference for the MPD operations.

Well control includes not only the handling but also early detection of a gas influx. Besides the transient pressure problem mentioned previously, investigation of the propagation characteristics of pressure wave is of great significance to the early detection of gas influx [19]. Many scholars believe that the pressure fluctuations procedure contains a wealth of information about the flow. Thus, characteristics of pressure wave can be easily used to measure some important parameters in the two-phase flow [20]. In the late 1970s, the former Soviet All-Union Drilling Technology Research Institute began to study characteristics of pressure wave propagation velocity in gas-liquid two-phase flow to detect early gas influx and achieved some important results [21]. According to the functional relationship between the pressure wave propagation velocity in gas-liquid two-phase flow and the gas void fraction, Li et al. [22] presented a method of detecting the gas influxes rate and the height of gas migration early after gas influxes into the wellbore. Furthermore, mud pulse telemetry is the most common method of data transmission used by measurement-while-drilling, and the transmission velocity of the pulse is a basic parameter for this kind of data transmission mode [23].

The pressure wave discussed in this paper can be transmitted as a pressure perturbation along the direction of flow in wellbore, which propagates with the speed of sound in the mud and gas two-phase drilling fluid. Due to the compressibility of the gas phase, the changes in interface between the gas and drilling mud, and the momentum and energy transfer between two phases, it is complicated to

predict the pressure wave velocity in gas and drilling mud two-phase flow. Since the 1940s, many experimental and theoretical studies have been performed. Experimental tests were conducted to inspect the contributions of fluctuation and flow characteristics on pressure wave. Ruggles et al. [24] firstly performed the experimental investigation on the dispersion property of pressure wave propagation in air-water bubbly flow. It was demonstrated that the propagation speed of pressure wave varies over a range of values for the given state, depending on the angular frequency of the pressure wave. Legius et al. [25] tested the propagation of pressure waves in bubbly and slug flow. The experimental result is similar to the calculation result of the Nguyen model and simulation result of the Sophy-2 package. Concluded form Miyazaki and Nakajima experiments [26] in Nitrogen-Mercury two-phase system, the slip between the phases plays a very important role in the mechanism of pressure wave propagation. From experimental investigation, Bai [27] found that the fractal dimension, correlation dimension, and the Kolmogorov entropy have close relationship with flow regime, and the fractal dimension will be greater than 1.5 when the flow is annular with high gas velocity. The characteristics of pressure wave propagation in bubbly and slug flow in a vertical pipe were investigated experimentally by Huang et al. in detail [28]. It confirmed that the propagation velocity is greatly affected by the gas void fraction and angular frequency of the pressure disturbance, and the superficial velocity of flowing medium has almost no effect on the propagation velocity. Also, there are some widely accepted models including elasticity model, homogeneous mixture model, and continuum model for pressure wave propagation in gas-liquid two-phase flow. Tangren et al. [29] took the two-phase media as a homogeneous fluid and presented the solution model concerning the problem of pressure wave velocity in two-phase flow at low gas void fraction. Wallis [30] studied the propagation mechanism of pressure waves and derived the propagation velocity in a bubbly flow and separated flow using the homogeneous model, in which the two-phase mixture is treated as a compressible fluid with suitably averaged properties. Nguyen et al. [31] applied the elastic theory to predict the propagation velocity of pressure waves in several different flow regimes. The comparison between the calculation results and available experimental data suggests its success at low void fraction. Mecredy and Hamilton [32] derived a detailed continuum model for sound wave propagation in gas-liquid flow by using six separate conservation equations to describe the flow of the vapor and liquid phases. This so-called two-fluid representation allows for nonequilibrium mass, heat, and momentum transfer between the phases. Results indicated that in a bubbly flow, high angular frequency waves travelled an order of magnitude faster than low angular frequency waves. With the development of hydrodynamics, the two-fluid model is widely used to determine the propagation velocity of the pressure wave in two-phase flow as it can provide a general dispersion relation valid for arbitrary flow regimes including effects of the interphase mass, heat, and momentum transfer. Ardron and Duffey [33] developed a model for sound-wave propagation in nonequilibrium vapor-liquid flows which

predicts sound speeds and wave attenuations dependent only on measurable flow properties on the basis of two-fluid conservation equations. Ruggles et al. [24], Xu and Chen [34], Chung et al. [35], Huang et al. [28], and Bai et al. [27] investigated the propagation velocity behavior of pressure wave via two-fluid model and small perturbation theory, and the predicted results show good agreement with the experimental data. In recent years, some new researches and models that are especially important in this area were developed. Xu and Gong [36] proposed a united model to predict wave velocity for different flow patterns. In this united model, the effect of a virtual mass coefficient was taken into consideration. The propagation of pressure wave during the condensation of R404A and R134a refrigerants in pipe minichannels that undergo periodic hydrodynamic disturbances was given by Kuczynski [37, 38]. Li et al. [39] simulated the condensation of gas oxygen in subcooled liquid oxygen and the corresponding mixing process in pump pipeline with the application of thermal phase change model in Computational Fluid Dynamics code CFX and investigated the pressure wave propagation characteristics in two-phase flow pipeline for liquid-propellant rocket based on a proposed pressure wave propagation model and the predicted flow parameters. Based on the unified theory of Kanagawa et al. [40], the nonlinear wave equation for pressure wave propagation in liquids containing gas bubbles is rederived. On the basis of numerical simulation of the gaseous oxygen and liquid oxygen condensation process with the thermal phase model in ANSYS CFX, Chen et al. [41] solved the pressure wave propagation velocity in pump pipeline via the dispersion equation derived from ensemble average two-fluid model. Li and He [42] developed an improved slug flow tracking model and analyzed the variation rule of the pressure wave along the pipeline and influence of the variation of initial inlet liquid flow rate and gas flow rate in horizontal air-water slug flow with transient air flow rate. Meanwhile, the compressibility effects of gas had been noticed in the research field of propagation of pressure waves in the drilling industry, and some efforts have been made. Li et al. [22] established the relationship between wave velocity and gas void fraction according to the empirical formula of the homogeneous mixture model presented by Martin and Padmanatbhan [43] and frequency response model presented by Henry [44]. By applying the unsteady flow dynamic theory, Liu et al. [45] derived the pressure wave velocity calculation formula for gas-drilling mud-solid three-phase flow based on the continuity equation. Wang and Zhang [46] studied the pressure pulsation in mud and set up a model for calculating the amplitude of pressure pulsation when pressure wave is transmitted in drilling-fluid channel especially drilling hose with different inside diameters. However some efforts have been made; the pressure wave velocity is usually determined by empirical formula. In the past researches, the influencing factors for pressure wave propagation were simulated and analyzed with the mathematical model; however, the variation of wave velocity and gas void at different depth of wellbore was not considered. In addition, the current researches are limited in their assumption and neglect the flow pattern translation and interphase forces along the annulus. Up to now, no complete

The object of the present work is to study the velocity for the transmission of pressure disturbance in the two-phase drilling fluid in the form of a pressure wave in annulus during MPD operations. In this paper, in addition to the pressure, temperature, and the void fraction in the annulus, the compressibility of the gas phase, the virtual mass force, and the changes of interface in two phases are also taken into consideration. By introducing the pressure gradient equations in MPD operations, gas-liquid two-fluid model, the gas-drilling mud equations of state (EOS), and small perturbation theory, a united model for predicting pressure wave velocity in gas and drilling mud in an annulus is developed. The model can be used to predict the wave velocity of various annulus positions at different influx rates, applied back pressures, and angular frequencies with a full consideration of drilling mud compressibility and interphase forces.

2.1. The Basic Equation. In this paper, the two-fluid model and the pressure gradient equation along the flow direction in the annulus are combined to study the pressure wave velocity in MPD operations. Drilling fluid contains clay, cuttings, barite, other solids, and so forth. The solid particles are small and uniformly distributed; therefore, drilling fluid is considered to be a pseudohomogeneous liquid, and the influx natural gas is considered to be the gas phase. The following assumptions are made:

As shown in Figure 1, the gas and drilling mud two-phase fluid travels along the annulus in the drilling process. The fluid flows along the annulus in "-z" direction, and the annulus is formed by the casing and drill string.

The interphase forces include virtual mass force, drag force, and the wall shear stress. The transfer of momentum between the gas and drilling mud phases MGi and MLi can be written as follows:

The proportion of gas phase in the interface between the gas and drilling mud is rather small in that the pressure difference between the gas interface and gas is not very high. Omitting the pressure difference, the gas interface pressure

2.2.2. Equations of State for Liquid. Under different temperatures and pressures, the density of drilling mud can be obtained by the empirical formulas.

2.2.3. Correlation of Temperature Distribution. The temperature of the drilling mud at different depths of the annulus can be determined by the relationship presented by Hasan and Kabir [51]:

2.3. Flow Pattern Analysis. Based on the analysis of flow characteristics in the enclosed drilling system, it can be safely assumedthatthe flowpattern in an annulusiseitherbubblyor slug flow [52]. The pattern transition criteria for bubbly flow and slug flow given by Orkiszewski are used to judge the flow pattern in the gas-drilling mud two-phase flow [53].

The total pressure drop gradient is the sum of pressure drop gradients due to potential energy change and kinetic energy and frictional loss. From (1), the equation used to calculate the pressure gradient of gas and drilling mud flow within the annulus can be written as

We can obtain pressure, temperature, gas velocity, drilling mud velocity, and void fraction at different annulus depths by R-K4. The solution of pressure drop gradient equation (41) can be seen as an initial-value problem of the ordinary differential equation:

In the present work, the mathematical model and pressure wave velocity calculation model are solved by a personally compiled code on VB.NET (Version 2010). The solution procedure for the wave velocity in the annulus is shown in Figure 1. At initial time, the wellhead back pressure, wellhead temperature, wellbore structure, well depth, gas and drilling mud properties, and so forth, are known. On the node i, the pressure gradient, temperature, and the void fraction can be obtained by adopting R-K4. Then, the determinant (45) is calculated based on the calculated parameters. Omitting the two unreasonable roots, the pressure wave velocity at different depths of the annulus in MPD operations can be solved by (47). The process is repeated until the pressure wave velocity of every position in the wellbore is obtained as shown in Figure 2.

The developed model takes full consideration of the interfacial interaction and the virtual mass force. Owing to the complex conditions of the annulus in MPD operations, measurement of wave velocity in the actual drilling process is very difficult. In order to verify the united model, the predicted pressure waves are compared with the results of previous simulated experimental investigations presented for gas and drilling mud by Liu et al. [45] in Figure 3(a) and by Li et al. [22] in Figure 3(b). The lines represent the calculation results, and the points represent the experimental data.

The drilling system described is an enclosed system. The schematic diagram of the gas influx process is illustrated in Figure 4. The drilling mud is pumped from surface storage down the drill pipe. Returns from the wellbore annulus travel back through surface processing, where drilling solids are removed, to surface storage. The key equipments include the following.

The gas and drilling mud flow rate measured by the Cori-olis meter and the back pressure measured by the pressure sensor are the initial data for annulus pressure calculation. The well used for calculation is a gas well in Xinjiang Uygur Autonomous Region, Northwest China. The wellbore structure, well design parameters (depths and diameters), gas and drilling mud properties (density and viscosity), and operational conditions of calculation well are displayed in Table 1.

The drilling mud mixed with gas is taken as a two-phase flow medium. The propagation velocity of pressure wave in the gas-drilling mud flow is calculated and discussed by using the established model and well parameters.

pressurized system. The pressure at different depths of the annulus varied with the change of back pressure. According to the EOS of gas and drilling mud, the influence of pressure on gas volume is much greater than that of drilling mud for the greater compressibility of gas. So, the gas void fraction changes with the variation of gas volume at the nearly constant flow rate of drilling mud at different annular pressures. Meanwhile, the pressure wave velocity is sensitive

to the gas void fraction. As a result, when the back pressure at the wellhead is changed by adjusting the choke, the wave velocity in the two-phase drilling fluid and the distribution of void fraction at different depth of the annulus will diverge. The calculation results affected by the back pressure are presented.

This can be explained from the viewpoints of mixture density and compressibility of two-phase fluid and the pressure drop along the flow direction in the wellbore. In the low void fraction range, the gas phase is dispersed in the liquid as bubble, so the wave velocity is influenced greatly by the added gas phase. According to the EOS, if gas invades into the wellbore with a small amount in the bottomhole, the density of the drilling mud has little variation while the compressibility increases obviously, which makes the wave velocity decreased. Then, the two-phase drilling mud flow from the bottomhole to the wellhead along the annulus with a drop of pressure caused by, potential energy change, kinetic energy and frictional loss, which leads to an increase in void fraction. When the void fraction is increased, both the density and the compressibility of the two-phase fluid change slightly, resulting in a flat decrease in wave velocity along the flow direction. With the further increasing in void fraction, the bubbly flow turns into slug flow according to the flow pattern transient criteria of Orkiszewski which shows that the flow pattern is dependent on the void fraction. Generally speaking, the gas-drilling mud slug flow is composed of liquid and gas slugs. In the preliminary slug flow, the liquid slugs are much longer than the gas slugs, so the wave velocity is determined primarily by the wave velocities in the liquid slugs which are hardly affected by the void fraction. At the position close to the wellhead, the pressure of two-phase flow fluid can be reduced to a low value which approaches the back pressure. The compressibility of gas will be improved at the low pressure. It results in significant increase in void

Figures 7 and 8 present the influence of back pressure on the void fraction and wave velocity with respect to the parameters of well depth. As the back pressure increases, the void fraction at different depth of the annulus is reduced gradually, while the wave velocity in the two-phase flow tends to increase. Analytical results show that the increased back pressure is equivalent to be applied to the entire enclosed drilling fluid cyclical system. The pressure transmits from the wellhead to the bottomhole; therefore, the annular pressure in the entire wellbore is increased. According to the EOS, the density of gas increases and the compressibility of gas decreases with the increasing of gas pressure. So, the loss of interphase momentum and energy exchange is reduced and the interphase momentum exchange is promoted. It contributes to the increase in wave velocity with the increase in gas pressure. In addition, due to lower compressibility of two-phase flow medium under high pressure, the increase tendency of pressure wave velocity and the decrease tendency of void fraction are slowed down in the high back pressure range.

5.2. Effect of Gas Influx Rate on Wave Velocity. Figures 9 and 10 graphically interpret the distributions of void fraction and variations of wave velocity along the flow direction in the annulus. When gas influx occurs in the bottomhole, gas invades into the wellbore and migrates from the bottomhole to the wellhead along the flow direction. At a low gas influx rate, it is extremely obvious that the void fraction and wave velocity first slightly change in a comparatively smooth value then change sharply. It is because of the rapid expansion of gas volume with the decreasing in pressure near the wellhead that the void fraction increases sharply, and the wave velocity decreases obviously at the same time. But under the high bottomhole pressure (up to 50 MPa), the compressibility of the gas is low. This results in a slight change in void fraction and wave velocity at the position far away from the wellhead. Since the compressible component increases with the increase in the gas influx rate, the compressibility of the gas and drilling mud two-phase fluid is improved. So the variations of void fraction and wave velocity become more prominent. Also, the void fraction still shows an increase tendency that is steady first and then sharp. It acts in accordance with the variation of void fraction at a low gas influx rate. At a low gas influx rate, if the void fraction at the position close to the wellhead can not increase to a high extent, the wave velocity always shows a decrease tendency. At a high gas influx rate, such as the Q = 8.312 m /h, the wave velocity tends to increase because the void fraction in the wellhead is increased to a high extent. In conclusion, the wave pressure is sensitive to the void fraction, and the void fraction is dominated by influx rate and pressure in the annulus, especially the influx rate.

With the influx of gas, the mixing of gas and drilling mud occurs in the annulus and the corresponding interfacial transfer of momentum and mass causes an increase in gas phase void fraction and a decrease in pressure wave velocity, as shown in Figures 11 and 12. Within the range of low gas influx rate, the wave velocity decreases significantly. It is because of this that the compressibility of the gas increases remarkably, and the medium appears to be of high elasticity, though the density of gas-drilling mud two-phase flow changes slightly. With the increase in the gas influx rate and corresponding increase in the void fraction in the annulus, the compressibility of the two-phase unceasingly increases, which promotes the momentum and energy exchange in the interface. So, the pressure wave continuously decreases. When the void fraction increases to some extent following the increase in the gas influx rate, the decrease in wave velocity in the liquid slug is gradually less than the increase in wave velocity in the gas slug; thus, the decrease of wave velocity is slowed down for the growth of gas slug. Especially in the wellhead, a slight increase in wave velocity is observed.

mass forces increases together with the increase of the relative motion in the interphase. It is evident that the bottomhole pressure is hundreds of times higher than the wellhead pressure. As a result, the void fraction at the position close to the wellhead increases sharply, meanwhile the interphase momentum and energy exchanges are promoted. The virtual mass force can be described as the transfer of momentum between the gas phase and drilling mud phase caused by the relative motion in the interphase. If the relative motion in the interphase is quite weak, the value of virtual mass force will intend to approach 0, and the influence on the wave velocity can be ignored. However, if the relative motion is rather intense, the effect of virtual mass force on the wave velocity should not be ignored. Furthermore, taking the virtual mass force into account, the dispersion characteristic of the pressure wave weakens obviously. Compared with the pressure wave velocity calculated by ignoring the effect of virtual mass force, the calculated pressure wave velocity with a consideration of the virtual mass force is lower. Therefore, it is necessary to analyze the effect of the virtual mass force on the wave velocity at the position close to the wellhead in MPD operations.

Figure 15 shows the effect of frequency on the wave velocity in the gas-drilling mud flow (Cvm = 0). The curves of the wave velocity of different positions reveal that the propagation velocity of pressure disturbances increases together with the growth of the angular frequency (0 < w < 500 Hz). It proves that the pressure wave has an obvious dispersion characteristic in the two-phase flow. As the angular frequency increases in the range of less than 500 Hz, there is sufficient time to carry out the exchange of energy and momentum between two phases. It achieves a state of mechanical and thermodynamic equilibrium between the two phases. So the wave velocity increases gradually with the increase in the angular frequency at different depths of the annulus. It is considered that the wave velocity is mainly affected by the interphase mechanical and thermodynamic equilibrium at low anglular frequencies. When the angular frequency reaches the value of w = 500 Hz, the pressure wave velocity achieves a constant value and remains on this level regardless of the further growth in angular frequency w. With the increase in angular frequency, there is not enough time for energy and momentum exchange between the gas-drilling mud two phases to reach the mechanical and thermodynamic

With full consideration of the important factors such as virtual mass force, drag force, gas void fraction, pressure, temperature, and angular frequency, a united wave velocity model has been proposed based on pressure drop gradient equations in MPD operations, gas-liquid two-fluid model, the gas-drilling mud equations of state, and small perturbation theory. Solved by the fourth-order explicit Runge-Kutta method, the model is used to predict wave velocity for different back pressures and gas influx rates in MPD operations. The main conclusions can be summarized as follows.

accurately calculate the wave velocity in the annulus. The application of the model will be beneficial to further study the wave velocity at different gas influx rates and back pressures in MPD operations, reduce nonproductive times, and provide a reference for the drilling operations in extremely narrow pore/fracture windows existing conditions.

(4)The wave velocity is sensitive to the void fraction, but the void fraction is dominated by gas influx rate and pressure in the annulus, especially the gas influx rate. Since the compressibility of the gas and drilling mud two-phase fluid is improved with the increase in the influx rate, the void fraction increases greatly, and the wave velocity decreases significantly within the low gas influx rate range. When the void fraction is increased to some extent following the increase in the gas influx rate, the decrease of wave velocity is slowed for the growth of gas slug. Especially at the wellhead, a slight increase in wave velocity is observed at a high gas influx rate for the sharp increase in void fraction.

A: Annulus effective cross area (m2) cG: Wave velocity in gas (m/s) cL: Wave velocity in Drilling mud (m/s) CD: The coefficient of drag force D: Annulus effective diameter (m) D ¡: Diameter of the inner pipe (m) D0: Diameter of the outer pipe (m) fG: Shear stresses coefficient of gas interface fL: Shear stresses coefficient of drilling mud interface

[2]P. Vieira, F. Torres, R. A. Qamar, and G. E. Marin, "Downhole pressure uncertainties related to deep wells drilling are safely and precisely ascertained using automated MPD technology," in Proceedings of the North Africa Technical Conference and Exhibition, Cairo, Egypt, February 2012.

[3]S. Saeed and R. Lovorn, "Automated drilling systems for MPD— the reality," in Proceedings of the IADC/SPE Drilling conference and Exhibition, San Diego, Calif, USA, March 2012.

[4]W. A. Bacon, Consideration of compressibility effects for applied-back-pressure dynamic well control response to a gas kick in managed pressure drillingoperations [M.S. thesis], University of Texas, Arlington, Tex, USA, 2011.

[6]J. A. Tarvin, I. Walton, and P. Wand, "Analysis of a gas kicktaken in a deep well drilled with oil-based mud," in Proceedings of the Annual Technical Conference and Exhibition of the Society of Petroleum Engineers, pp. 255-264, Dallas, Tex, USA, 1991.

[8]J. Zhou and G. Nygaard, "Automatic model-based control scheme for stabilizing pressure during dual-gradient drilling," Journal ofProcess Control, vol. 21, no. 8, pp. 1138-1147, 2011.

[9]A. Ochoa, O. Acevedo, L. Nieto, J. E. Lambarria, and H. Perez, "Successful application of MPD (Managed Pressure Drilling) for prevention, control,and detection of borehole ballooning in tight gas reservoir in Cuervito Field, Mexico," in Proceedings of the Canadian Unconventional Resources Conference (CURC "11), pp. 172-185, November 2011.

[10]P. Vieira, F. Torres, R. A. Qamar, and G. E. Marin, "Downhole pressure uncertainties related to deep wells drilling are safely and precisely ascertained using automated MPD technology," in Proceedings of the North Africa Technical Conference and Exhibition, Cairo, Egypt, February 2012.

[12]S. Wang, C. Qiang, and K. Bo, "Fluctuating pressure calculation during the progress of trip in managed pressure drilling," Advanced Materials Research, vol. 468-471, pp. 1736-1742, 2012.

[13]I. Zubizarreta, "Pore pressure evolution, core damage and tripping out schedulesf: a computational fluid dynamics approach," in Proceedings of the SPE/IADC Drilling Conference and Exhibition, , Amsterdam, The Netherlands, March 2013.

[15]G. M. de Oliveira, A. T. Franco, C. O. R. Negrao, A. L. Martins, and R. A. Silva, "Modeling and validation of pressure propagation in drilling fluids pumped into a closed well," Journal of Petroleum Science and Engineering, vol. 103, pp. 6171, 2012.

[18]W. Bacon, A. Tong, O. Gabaldon, C. Sugden, and P. V. Surya-narayana, "An improved dynamic well control response to a gas influx in managed pressure drilling operations," in Proceedings of the IADC/SPE Drilling Conference and Exhibition, San Diego, California, USA, March 2012.

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Multilateral-horizontal-well drilling is an efficient approach for stimulating shallow, low-permeability, marginal, and coalbed-methane (CBM) reservoirs. Radial-jet-drilling (RJD) technology, which uses a high-pressure water jet, aims to drill tens of laterals from a vertical wellbore. Hydraulics design is essential for successful field-drilling operations. However, detailed hydraulics calculations and design methods have not yet been published.

The hydraulics calculations corresponded well with the field data. The model error was within 8%. The pressure loss of the high-pressure hose and jet bit represents a large proportion of the RJD-system pressure loss (41.2 and 55.8%, respectively). According to the operation profile, the calculated pump pressure will help the field engineer to estimate the working status of downhole tools. The results show that the pump flow rate should be optimized for different well configurations. The optimum flow-rate range was determined by the minimum lateral-extending force, minimum rock-breaking jet-bit-pressure drop, and minimum equipment-safety working pressure. To maximize the rate of penetration (ROP), the largest flow rate within that interval was selected as the optimum flow rate. A flow rate of 57.24 L/min was optimal for the case well.

Mud Pump Valve & Seat are made of premium alloy steel through one-piece forging and carburizing treatment processes, thereby ensuring high intensity. In addition, the precise calculation is performed and CNC machining is conducted for the dimensional matching of the valve seat and valve body working angles to enhance the service life of the valve body and valve seat. Our valve products are able to work smoothly in normal mining and digging conditions for over 400 hours.

REASON: This is the mud engineers Bible on the rig. It is based on prior knowledge of all drilling parameters and gives you a step by step plan for present well being drilled. It would guide you all though the drilling process.

Study your silos, pits, mud tanks, storage tank names, its contents, volume, dead volume capacity, properties of their contents (mud: especially Mud weight).

REASON: You don’t want to be taken unawares, you need to know the type of mud you have in each pit (where your backup mud is, kill mud if any, premix, etc.), you need to be sure you have enough mud to reach TD (Total depth) most especially if the logistics of transporting mud to the rig n’est pas facile, or takes days to arrive. Finally without knowing the properties of the mud you are introducing to the active system you would not be sure if what is affecting your active mud system is coming from the formation or from the mud you are introducing to the active mud.

REASON: You need to be sure the shaker screens can handle the flow if the mud is cold if not temporarily screen down to a lower size mesh or ask the driller to reduce the flow rate if permissible.

REASON: Drilling fluids would normally splash the rig crew on the rig floor while pulling and racking back pipes when a stand is removed from the drill string. So a slug (same mud but with 2-2.5 ppg higher density) would be prepared in the slug tank, and pumped into the drill string. This keeps the fluids level inside the drill pipe below the surface when tripping drill pipe.

For a leak off test (LOT), the mud has to be circulated to obtain uniform weight and condition. The primary concern for the mud engineer is to ensure an equal mud weight all through the mud. Mud weight going in to the hole should be equal to mud weight coming out of the hole at the shakers.

REASON: The well needs to be properly monitored. Instead speak with the mud loggers to convert the pit you want to transfer fluid from to the active system from a Reserve pit to an Active pit on their system then you can gradually make your transfers that way all volumes would be shown as active pit volume.

REASON: If the amount and average specific gravity of the solids in both fluids (i.e. the density) are different the mud weight would be a good indicator of the fluids interface during a displacement.

REASON: Calculate your hole volume, that means equal amount of mud on surface will leave you pit, so get the derrick man or personnel assisting you in the pit room to inform you when hole volume has been pumped.

REASON: Using a technique called nephelometry the turbidity can be measured. When light hits a particle the energy is scattered in all directions, it measures the level of light scattered by particles at right angles to the incident light beam. Initial NTU readings of both fluids would be the reference point for identification. After the Hi-vis passes through the driller should be told to stop pumping when the initial NTU of the filtered brine has been achieved.

For water based mud with a low alkalinity use phenolphthalein also. Add it to the mud and check for change of color to pink to know when traces of cement are on surface.

REASON: Note differences in weight between mud, spacer and cement before displacement of cement. The mud weight difference between the three fluids is a good indicator of the fluids interface on surface.

REASON: The first step is removal of cuttings from the borehole and the drilling fluid after which the mud should be condition before placing cement in the wellbore, either the density (not compromising well control) or the rheology depending on the situation. For the rheology, the yield stress, gel strength and plastic viscosity would be reduced hence reducing the driving forces necessary to displace mud with increased mud flexibility while being careful to prevent barite settling.

REASON: With no pit space to store the equivalent mud volume being replaced down hole, all pit levels should be recorded at all stages during the cement job. You would need to visit the pit room and return to the cement unit (while measuring cement density) at appropriate moments.

Measure all tank volumes before cement job i.e. when the mud has been thinned down and pump has been stopped (pit static). In case of leaks or valve mistakes all pits should be recorded.

If we get full returns during cementing it means that the cement displaced equal amount of mud and there was no loss down hole due to the cement job or due to displacement.

Prior to running casing, calculate the displacement of the casing first to know the volume it would displace, calculating from the mud line up to the casing depth.

REASON: From the cement program calculate the total volume of the fluids /cement that would be pumped into the hole that is not mud so as to confirm tank space to receive equal volume from the hole. If no available tank space/storage space then OBM should be back-loaded before the cement job to create space.

REASON: If it’s the pay zone, losses would require the use of acid-soluble LCM to prevent formation damage. Also considering down hole tools and motors, certain concentrations of LCM pills would not be pumped to avoid plugging/damaging the tools unless a bypass tool is part of the BHA.

REASON: To observe nature of cuttings while drilling- If cuttings are round, splintered, tabular, marshy, brittle, if no cuttings, if shakers are clean at TD prior to pulling out of hole. After your assessment of the cuttings then you decide what action to take.

Bit balling occurs in soft gumbo / swelling shales while drilling, the shale adsorbs water from the mud it then becomes plastic with a ball of compacted shale building up and covering the whole bit, stabilizers and drill collars, thus preventing further drilling progress.

To be certain it’s a bit balling issue we are dealing with the mud engineer should observe some of the following or collect the following information from the following rig personnel, with the first 3 information from the driller being very important:

Selecting a bit with a center jet “C”. Center jets are designed to help prevent bit balling by cleaning the cutters in larger diameter bits drilling soft formations.4

To prevent bit balling from occurring it is advisable to adopt procedures that worked in your geographical area in overcoming bit balling by always reviewing previous drilling mud report (DMR).

· Use mud system that can inhibit clay swelling example: Formulating KCl mud with PHPA (to avoid using higher concentrations of KCl) in which KCl prevents clay swelling while PHPA (partially hydrolyzed polyacrylamide ) coats the shales surfaces (encapsulates) thereby inhibiting their dispersion and incorporation into the mud.7

· “When drilling gumbo, the pH should be maintained at 9.0-10.0. If bit balling occurs, increase the mud alkalinity (PM) to 5 or more with lime”.8

· Use drilling detergent, they are a specific type of dispersant that helps prevent formation of shales and clay from sticking to the drilling assembly and prevents agglomeration and plugging of the annulus by gumbo shale. They reduce occurrences of bit balling9, help in reducing the drag and torque of the drill string when it is rotated and moved up and down.

· “If all else fails, before you trip out of the hole, you might pump a walnut-hull sweep. It will tend to sandblast the bit and remove the ball, and won’t hurt the mud. Don’t try this if you are running small jets in the bit, as plugging can be an issue.”11

A Drilling fluids Engineer should be able to observe or carry out a test and subsequently identify the reason for a high or a low mud weight in a water-base mud or an oil-base mud system.

Before looking at the reason why the mud weight reduced or increased from the given mud program specification, it’s good to know that the major function of drilling fluids is to provide sufficient pressure to check influx of gas, oil, and water into the well bore from the drilled formation.

The hydrostatic head of the mud column must be at least equal to that of the formation pressure, and hopefully greater, but not so high as to cause loss of circulation (except where an over balanced / under balanced drilling are specifically desired).

The mud weight materials could be barite, calcium carbonate or soluble salts such as sodium chloride (NaCl), potassium chloride (KCl) and calcium chloride (CaCl2). Sometimes the desired mud weight can be achieved by combining additions of salts and barite.

a. Mud Weight (Density) Test: The mud balance may indicate that mud weight is too high or too low. b. Retort Test: The test may indicate that the percent solids by volume is high, and your solids content calculations (lb/bbl low and high gravity solids) may indicate that barite content is too high or too low. c. Rheology tests: Indicates increase or decrease in viscosity

a. Increase in pump pressure: This can indicate an increase in Mud weight. b. Change in penetration rate: Increase in penetration rate may indicate decrease in mud weight while decrease in penetration rate may indicate increase in mud weight. c. Gas bubbles: This definitely indicates decrease in mud weight.

Triplex: This mud pump is used for drilling applications needing high pump pressure. This model works by decreasing the working fluid volume being discharged to generate pressure for producing the flow. There are three pistons in the triplex pump, with the middle piston generating more pressure on the crankshaft. High piston load can lead to excessive pressure and crankshaft failure if the components are not properly sourced.

Quintuplex:Quintuplex mud pump is perfect for pumping fluid at the time of drilling operations. It works as a continuous duty return piston. This is used in terms of its external bearings to provide crankshaft support to ensure the proper functioning of the sheaves.

Duplex: These mud pumps ensure that the mud circulation reaches the well"s bottom from the mud cleaning system. Duplex pumps have binocular floating seals as well as safety valves.

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