Sucker Rod Pumping System Research Articles

Approach to the Design Calculation of Sucker Rod Pumping Systems in Coalbed Methane Wells

The existing design of the pumping systems mainly focuses on the approximate computational formulae and procedures,which are developed based on the analytic approaches of conventional oil/gas fields.The calculation of polished rod loads usually just concerns about the static and inertial loads.And the computation of gearbox torque generally uses empirical formulae and correction factors.The above modeling procedures,if applied to the coalbed methane(CBM) wells,can not give the desired accuracy of the system design and its pertinent analysis.In this paper,based on the kinematic and dynamic analysis of the pumping system,the kinematic relation of polished rod is analyzed,and the variation of the total loads of polished rod is developed with the limits of CBM well conditions along the string.The gearbox torque calculation model is established by combining the counterbalance effect with the calculated dynamometer cards and torque factors.The application characteristics of this model are demonstrated by the example of ZH002-4 well in Qinshui basin.The interpretations of results show that the cranks of beam units should rotate in a counter clockwise direction viewed with the wellhead to the right.Compared with oil?gas fields,the dynamic and friction to polished rod load ratios are relatively high and the computation of polished rod loads should involve the static and inertial loads,as well as vibration and friction loads.And the dynamic load ratio decreases rapidly during the production.Besides,the total deformation of the string is small in CBM wells.As for balanced operation,the gearbox torque load usually has two approximately equal peaks and the magnitudes of instantaneous torque are just within 50% of unbalanced gearbox loadings.The proposed research improves efficiency of the pumping system,loads the pumping unit more uniformly,and provides the reasonable basis for selecting the units.

Variation of Polished Rod Loads for Sucker Rod Pumps in Coalbed Methane Wells

Polished rod load is an important parameter to illustrate the operating potential of sucker rod pumping system.Based on the kinetic characteristic of the pump,the mathematical models of polished rod loads and dynamometer cards are obtained in coalbed methane(CBM) wells.Then the variation of polished rod loads and the string deformation are developed by applying the method.The results show that the computation of polished rod loads should consider the vibration and friction loads.The variation range of polished rod load is large due to the heavy water drainage during the prophase while it is small during the steady flow production.The dynamic and friction to polish rod load ratios are calculated to be 15% and 5%,respectively,which increases the variation range.The static load ratio enhances gradually,and the dynamic load ratio decreases rapidly during the prophase and is just 2.5% during the steady flow production,while the friction load ratio becomes 3.7%.Besides,the total string deformation in CBM wells is just 10% of stroke length,which is much smaller than that in oilfields.And the static deformation is relatively large while the dynamic deformation is small in the total deformation.A mathematical model and dynamometer card for the sucker rod pumping system as the result of this work will provide the reasonable basis for designing and selecting sucker rod pumps.

Dynamic Analysis of the Sucker-Rod Pumping System of Deviated Well Based on LuGre Friction Model

Based on the LuGre friction model, the nonlinear dynamic characteristic of a sucker-rod pumping system of deviated well is simulated. Firstly, the LuGre friction model is introduced, and the values of its six model parameters, which satisfy the engineering’s needs, are obtained according to handbook and computation. Then, the vibration of the rod of sucker-rod pumping system is regarded as an axial vibration of multi-segment flexible rod. The loads analysis of rod element is accomplished by means of the finite element method, and recurrence formulas of load and elastic deformation are derived through the finite difference method. The boundary and initial conditions of the load and deformation are evaluated. In the end, a numerical example is given, where a comparison between the elastic deformation of pumping piston obtained based on LuGre friction model and that obtained based on classical Coulomb friction model is made to show that the LuGre friction model describe the friction of sucker-rod pumping system better.

Calculation of dynamic loads of the sucker rod pumping system in CBM wells

The mathematical model of dynamic loads was developed based on an analysis of the polished rod load of beam pumps, and the variation of the dynamic loads and the computation of the minimum and maximum limits during a complete pumping cycle were given out by solving the model. Field examples verify that it is necessary to take into account the inertial and vibration loads while calculating polished rod loads. During the prophase of the pumping production, the dynamic to polished rod load ratio is relatively large. Then the ratio decreases rapidly and becomes small after entering stable production. Moreover, the total deformation of rod and tubing in CBM wells is much smaller than that in oil fields, and the deformation caused by the dynamic loads is also relatively small. The result of this work is the calculation of the dynamic loads. The application of this calculation for the sucker rod pumping system in CBM wells can give the desired accuracy of polished rod load and the dynamometer cards, which provides a reasonable basis for the design and selection of beam pumps.

Model Reference Adaptive Control Applied to the Improvement of the Operational Conditions of a Sucker Rod Pump System

Several studies have shown that the satisfactory operation of oil wells with sucker rod pumps is attributed to the techniques and methods able to control the performance of the well. The Polytechnic School of Federal University of Bahia, through the Artificial Lift Lab, has nowadays a reduced plant of a sucker rod pump with an artificial well of 32m height fully instrumented, with full access and visible. Among some studies already performed with this sucker rod pump, there is the use of a dynamic model to control the fluid level in annular well. The presence of uncertainties is related to the fluid characteristics in the well, associated with either the electrical or the mechanical assembly, may jeopardize the desired performance of the PID controller. These uncertainties usually do not contribute to good results and may put in risk the well's productivity. The aim of this paper is to show a model reference adaptive controller to deal with some uncertainties in the system model to control the level of the annular well. The results show that the adaptive controller is able to deal satisfactorily with changes, such as: in the pumped fluid composition (parts of water, oil and gas), which is a very common situation in real production fields.

Sucker-Rod Pumping System Fault Detection and Isolation Method Using Bottom Hole Pressure Measurement

In this paper a framework proposal is presented for fault detection and isolation based on principal component analysis for sucker-rod pumping systems using bottom hole pressure and others measurements. The proposed algorithm uses signals frequency attributes to generate faults signatures. Hotelling's T2 index and the square prediction error are used to compare process online samples with signatures generated offline. The results were obtained using a sucker-rod pump simulated model.

Downhole Gas Separators-A Laboratory and Field Study

Abstract Downhole gas separators are often the most inefficient part of a sucker rod pump system. This paper presents laboratory data on the performance of five different gas separator designs. Only continuous flow was studied. Field data is presented on one of the designs. The field data indicates that success or failure of the gas separator is dependent upon the fluids and wellbore pressures, as well as the mechanical design of the gas separator. Successful and unsuccessful examples of gas separator performance in the field are shown along with field fluid data properties. While the study is not complete, this is the first of hopefully several papers that will present the results of this investigation. Introduction Patterson and Leonard(1) studied different downhole gas sep-aration designs for coalbed methane operations in Wyoming. In these designs, the inlet to the gas separators were smaller than normally used and, along with some baffles (thought to allow gas to vent from inside the gas separator), obtained good gas separation in the field installation. It was these installations which prompted the laboratory study of the gas separator geometry to understand if the ‘rules-of-thumb’ used by the industry for gas separator design were valid. The objectives of this paper are to give a clearer insight into the mechanisms of gas interference in pumping wells and to present the results of recent laboratory and field studies on the flow characteristics and performance of some downhole gas separators. In these applications, the separation of gas from liquid is achieved through gravity separation without the introduction of other mechanisms (centrifugal forces, nozzles, etc.). Thus, the difference in density between the gas and liquid is the main driving force for separation. This implies that forces that oppose the effect of gravity, such as viscous drag caused by high fluid velocity and turbulence, will be detrimental to the separation process. Thus, high velocity of liquid or gas should be avoided, if possible. The Pumping Wellbore as a Gas-Liquid Separator The preferred pumping installation for maximum pump efficiency requires installing the pump intake below the lowest point of fluid entry into the wellbore and requires having an open casing-tubing annulus from the bottom to the wellhead. Gas and liquid enter the wellbore through the perforations and liquid flows to the bottom of the well under the action of gravity. The lighter gas bubbles rise through the liquid, forming a gaseous liquid column from the bottom of the perforated interval to the fluid level. Then, gas flows through the casing-tubing annulus to the wellhead where it exits to the flow line. Practically 100% liquid accumulates at the bottom of the well and enters the pump intake to be discharged by the pump into the tubing. In a large number of wells, it is not possible to install the pump intake below the lowermost fluid entry point in the wellbore. Typically, this is caused by an insufficient rathole, the presence of liners or gravel packs, concerns regarding sanding up and sticking the pump or just the operator's preference.

Identification for Sucker-Rod Pumping System’s Damping Coefficients Based on Chain Code Method of Pattern Recognition

In this paper, a method for identifying the damping coefficients of a directional well sucker-rod pumping system is put forward by means of the chain code method of pattern recognition. The 24-directional chain code is provided to encode the dynamometer card curve. The parametric equation of the dynamometer card curve is transformed into Fourier series whose coefficients can be computed according to the curve’s chain codes. By means of these coefficients, shape characteristics of the curve are extracted. The Euclidean distance is introduced as the measurement of similar degree between the shape characteristics of measured dynamometer card and that of simulated dynamometer card. Changing the value of viscous damping coefficient and Coulomb friction coefficient in the simulation program, different simulated dynamometer cards are obtained. Substituting their shape characteristics to the Euclidean distance, respectively, a series of distances are acquired. When the distance is less than the given error, the corresponding values of the damping coefficients in the simulation program are regarded as real damping coefficients of the sucker-rod pumping system of directional well. In the end, an example is provided to show the correctness and effectiveness of the presented method.

A Laboratory Study With Field Data of Downhole Gas Separators

Summary Downhole gas separators are often the most inefficient part of a sucker-rod pump system. This paper presents laboratory data on the performance of five different gas-separator designs. Only continuous flow was studied. Field data are presented on two of the designs. The field data indicate that success or failure of the gas separator is dependent upon the fluids and wellbore pressures as well as the mechanical design of the gas separator. Successful and unsuccessful examples of gas-separator performance in the field are shown along with field fluid data properties.

Application of self-organizing competitive neural network in fault diagnosis of suck rod pumping system

This paper represents a study using Artificial Neural Network (ANN) to solve dynamometer cards auto recognition problem. A self-organizing competitive neural network model is constructed to achieve automatization of fault diagnosis by automatically clustering dynamometer cards. Model is trained and tested using data acquired from Jiangsu oil fields, China. Research results show that self-organizing competitive neural network model has good classification and generalization capabilities, and hence is applicable to the automatic fault diagnosis of suck rod pumping system.

Ameliorative characteristic recognition method based on modified chain code and its application in damping coefficients identification for rod pumping system

Aimed at the shortcomings of the eight-directional Freeman chain code method, a new 24-directional chain code is put forward to encode the closed boundary curve of an image. The parametric equation of the closed boundary curve is transformed into Fourier series whose coefficients can be computed according to curve's chain codes. By means of these coefficients, shape characteristics of the boundary curve are extracted. The Euclidean distance based on shape characteristics is introduced as the measurement of similar degree between two different closed boundary curves. Changing the value of viscous damping coefficient and Coulomb friction coefficient in the simulation program, different simulated dynamometer cards are obtained. Substituting their shape characteristics to the Euclidean distance, respectively, a series of distances are acquired. When the distance is less than the given error, the corresponding values of the damping coefficients in the simulation program are regarded as real damping coefficients of the sucker-rod pumping system of directional well. In the end, an example is given to show the correctness and effectiveness of the presented method.

Fundamental Equations for Dynamic Analysis of Rod and Pipe String in Oil-Gas Wells and Application in Static Buckling Analysis

Abstract A large number of string materials, such as drillstring, pumping rod, tubing, coiled tubing, casing, etc., are used in oil and gas drilling and production. Proper mechanical analyses of these strings are important. This paper analyses the motions of these strings, and establishes the fundamental equations for the dynamic analysis of these strings in oil and gas wells. The fundamental equations have successfully unified all of the differential equations used in the dynamic analysis of rod and pipe strings in oil and gas wells. All of the differential equations present used in the calculation of tension and torque in directional wells, analysis of drillstring vibration, analysis of bottom hole assembly (BHA), analysis of the buckling behaviour of pipe and casing strings, and analysis of sucker rod pumping systems can be obtained just by proper simplification of the fundamental equations. Thus, these equations have broad uses in drilling and production. The buckling of coiled tubing string, drillstring and casing etc., plays an important role in oil drilling and production operations. As a very important application of the fundamental equations, this paper also establishes the differential equations for the buckling of the strings in inclined straight holes. The linear and non-linear mathematical models for buckling of these strings in horizontal sections have been established. The critical forces for helical and sinusoidal buckling in inclined straight holes have been found. The linear and non-linear buckling of the weightless strings has been analysed. Other applications of the fundamental equations in drilling and production have been presented. Introduction Since the pioneering work by Lubinski et al.,(1) the drilling and production industry has gradually come to accept and appreciate the importance of analysis of BHA, drillstring, casing, tubing, pumping rod etc. A large number of differential equations have been established for special analysis(1–20). However, no fundamental equations that unify these differential equations have been established. As an attempt, this paper establishes the fundamental equations for the dynamic analysis of drillstring, BHA, casing, tubing, pumping rod, etc. in oil and gas wells. Lubinski et al.(1) defined the helical buckling behaviour of pipes in vertical wells. However, the post-buckling behaviour of pipe in inclined and horizontal wells is different from that in nearby vertical wells. Knowledge of the configuration of buckled tubular is important to prevent costly failures, to predict whether a tool can be forced along a directional or horizontal well, and to optimize the tubular string. As an important application of the fundamental equations, this paper also establishes the differential equations for the buckling of the string in inclined straight holes. The linear and non-linear mathematical models for buckling of these strings in horizontal sections have been established. The critical forces for helical and sinusoidal buckling in inclined straight holes have been found. The linear and non-linear bucking of the weightless strings has been analysed. Fundamental Equations for Dynamic Analysis of Rod and Pipe String in Oil-Gas Wells Motions of Strings in Oil and Gas Wells

Design and Optimization for Sucker Rod Pumping System in Deviated Wells

Design and Optimization for Sucker Rod Pumping System in Deviated Wells

98/00858 A simple model for computer-aided optimization and design of sucker-rod pumping systems

98/00858 A simple model for computer-aided optimization and design of sucker-rod pumping systems

A simple model for computer-aided optimization and design of sucker-rod pumping systems

Design or optimization of a sucker-rod pumping system requires an evaluation of the system performance under different operating conditions. The precise evaluation of the performance is a complex task. A dynamic behavior of the sucker-rod string and complex interactions between components of the system and fluids in motion have to be taken into consideration. In this paper, a simple model of a sucker-rod pumping system is presented, and performance and applications of the model are outlined. A comprehensive, mathematical model of the system accounts for fluid and rod string dynamic behavior. Approximate surface and downhole dynamometer cards, production rates, downhole and surface forces, and energy consumption of sucker-rod pumping system are simulated with high accuracy for a variety of operating conditions. The model is defined by a system of linear algebraic equations derived from the straightforward Bergeron method rather than from numerical differentiation of wave equations. Example results of modeling indicate a good agreement with field data. The model was used to optimize an existing sucker-rod pumping system. Example results indicate significant savings over unoptimized operation. The model may also have an application at the design stage of the sucker-rod system development. The outline of the design procedure with application of the new model is presented.

An alternative approach to the analysis of sucker-rod dynamics in vertical and deviated wells

A set of partial differential equations which consider the combined effects of fluid column, sucker-rod string and tubing motion were developed to describe the motion of a sucker-rod pumping system. If the tubing is fixed, only the fluid column and rod motion need be considered; however, when the tubing is free to move, energy in the system is lost and, therefore, pump system efficiency declines, hence, the need to consider these effects in the design of the sucker-rod system. Using finite differences this model was used to evaluate performance of sucker-rod pumps (pumping rate as a function of number of strokes, stroke length, rod length, ratio of plunger to cylinder diameter, etc.) in both vertical and deviated wells. The results indicate that the developed model simply and accurately models the dynamic motion of the sucker-rod string. The examples presented illustrate its general applicability in both vertical and deviated wells.

A Coupled Rod and Fluid Dynamic Model for Predicting the Behavior of Sucker-Rod Pumping Systems—Part 1: Model Theory and Solution Methodology

Summary Equations are derived from first principles for predicting the behavior of sucker-rod pumping systems including the effects of rod and fluid dynamics, and kinematics of the surface pumping unit. Equations are also developed for both incompressible and slightly compressible fluid flow scenarios. The resulting composite rod and fluid dynamic model is solved using the MacCormack Explicit Numerical Scheme. Example problems used to validate this model are presented in a companion paper.

A Coupled Rod and Fluid Dynamic Model for Predicting the Behavior of Sucker-Rod Pumping Systems—Part 2: Parametric Study and Demonstration of Model Capabilities

Summary Equations for predicting the behavior of sucker-rod pumping systems including the coupled dynamic effects of rod and fluid motion and kinematics of the surface pumping unit which were presented in Part I of this two-part paper series. These equations are used together with complementary sucker-rod system predictive formulas for parametric studies in this paper. Example problems are used to investigate the effects of well and fluid parameters on sucker-rod design parameters and the results are compared against calculations using the API Bulletin 11L3.

Application of Artificial Neural Network to Pump Card Diagnosis

Abstract Beam pumping is the most frequently used artificial lift technique. Down hole pump cards are used to evaluate performance of the pumping unit. Pump cards can be generated from surface dynamometer cards using one-dimensional wave equation with viscous damping, as suggested by Gibbs. Pump cards contain significant information describing the behavior of the pump. However, interpretation of these cards is very tedious and time consuming. Hence, an automated system capable of interpreting these cards is very useful. This work presents a DOS based computer program capable of correctly classifying pump cards. The program uses a hybrid artificial neural network (ANN) to identify significant features of the pump card. The hybrid ANN utilizes classical and sinusoidal perceptrons. The network is trained using error back propagation technique. The program has been able to correctly identify problems in over 100 different training and test pump cards. The ANN requires total of 80 data points as input. Sixty data points are collected from the pump card perimeter itself and the remaining 20 data points represent the slope at selected points on the pump card perimeter. The problem conditions are grouped into distinct classes such as malfunction anchor tubing, fluid pound, gas interference, and worn traveling valve. The network is capable of identifying one or more of these problem conditions for each pump card. Several examples will be presented and discussed. Introduction Sucker-rod pumping system is a very popular means of providing artificial lift for wells. It is estimated that 90 percent of artificially lifted wells use sucker-rod pumping systems. In order to assure proper operation of these systems it is necessary to monitor them on a regular basis. This is done by means of a dynamometer which is attached to the polished rod of the pumping unit. The plot of load versus position generated by the dynamometer is known as a surface card. Using the technique proposed by Gibbs this surface card can be used to obtain down hole "pump card". The pump card presents the load versus position at the pump down hole instead of the load versus position at the polished rod on the surface. The shape of the pump card can be used as a diagnosis tool. For example, when the pump is functioning properly and pumping to its full capacity the pump card will have a rectangular shape. When the pump capacity is not being fully utilized then we may have a condition called "fluid pound". The petroleum industry is in the process of automating the control of pumping wells. Computers are being used to continuously monitor the pump and transmit data to a central office for further analysis. The shear volume of data received makes it necessary to develop tools for automatic analysis of the pump cards. Various pattern recognition techniques have been used to analyze the down hole pump card. Traditional techniques require significant processing time. P. 151^

Periodic motions of sucker rod pumping systems

AMONG the most important of the artificial lifting methods used in petroleum industries are the sucker rod pumping systems. In order to improve the design and the operation of such installations, it is necessary to understand their behavior, especially at infield situations. The pumping system is put into action by an engine that imparts a periodic motion to the top of the rods, and eventually all of the system sets itself in a periodic motion. To describe this behavior, several mathematical models have been developed over the years by taking into consideration various inertial and dissipation effects in the system, material properties, down hole pumping conditions, fluid interactions, and so on (see for instance Doty and Schmidt [l]). Obviously, several nonlinearities are present in the problem, but there is one that is intrinsic to the pumping system itself. This is due to the presence of the valve mechanism that imposes sudden changes in the stress acting on the rods according to the opening or the closing of the down hole and walking valves. Concerning the study of these models, some theoretical analysis has been done in certain linearized versions of the models, and many numerical experiments were performed. In general, however, there is a lack of sound mathematical analysis of the nonlinear models. In this paper we consider a simple model that takes into consideration the elastic response of the rods, the dissipation mechanism (due to internal material dissipation and hydraulic friction) and the stress change due to the valve mechanism. It corresponds to the same partial differential equation used in Pavlik and Schafer [2], it is a wave equation with dissipation, but with a nonlinear and discontinuous boundary condition modeling the action of the valves. Our objective is to study the interaction between the action of the valves with the periodic motion imparted by the engine on the top of the rods in the production of the final motion of the rod. We are able to show the existence of a strong forced periodic solution for the mathematical model of this problem in the following way: we first show that the operator associated to the problem is maximal monotone in a convenient Hilbert space. Thus, we are in the setting of the well-known theory of monotone operators, but we cannot apply its standard results on periodic solutions because our operator is neither strictly monotone nor coercive. The main difficulty is to control the influence of the boundary conditions. We then proceed by approximating our equation in a suitable way by equations for which the corresponding operators are strictly coercive; for them the standard theory can be applied, and approximated periodic solutions are obtained. We then strive to obtain certain estimates for these approximated solutions, which permit us to conclude that they approach a mild periodic solution of the original problem. An essential step for this is the construction of an adequate Liapunov function that furnishes an