Rod String Research Articles

PREVENTING THE ROD STRING REVERSE BY APPLYING FLEXIBLE COUPLING GROUP AND ANAEROBIC HERMETICAL MATERIALS IN BASHNEFT-PRODUCTION Ltd

Currently, the main goals in the field of oil and gas production include costreduction and reduction of production losses due to increased efficiency of operation of the mechanized well stock. At the fields of Bashneft Production Ltd, the production of oil wells is operated mainly by means of sucker-rod well pumping units, therefore, increasing the efficiency of this method of oil production is a priority task. The proposed article discusses the analysis of well stock failures due to the top of the rod string and the main causes of the cuffs, as well as measures developed and implemented to reduce the number of failures due to the top of the column string.

Diagnostics of the condition of sucker-rod pumping units after the analysis of dynamogram cards

Despite of the increased share of oil wells equipped with submersible electrical centrifugal pumps, a considerable part of them is equipped and operated with sucker-rod pumping units. When operating wells with sucker-rod pumping units, different plunger pumps are used. The rod string is operated in severe environment due to long contact with highly corrosive well products and time-variant loads. Taking into account all acting loads, the diagnostics of the condition of sucker-rod pumping units is a difficult task. At the majority of oil fields in Russia, the operation of wells equipped with sucker-rod pumping units is controlled by portable and stationary dynamographs of various models. Moreover, dynamographs are used, as a rule, only to obtain images of dependence of the force on the polished piston rod upon its stroke. Based on dynamograms it is possible to find the well flow rate, pump capacity, force on the polished piston rod, etc. But one of the main problems to be solved with the help of dynamometry is the forecasting of down-hole equipment condition in the process of further operation. In this paper we overview the methods to diagnose the condition of sucker-rod pumping units based on dynamograms. The aim of the work is to develop the mathematical model to forecast the failures of down-hole pumping equipment on the results of dynamometry to automatize the control process of the unit operation. The research tasks are to analyze the existing methods for diagnosing the condition of sucker-rod pumping units, and to develop the mathematical model for forecasting the failure of the valve unit leakage. As a result, the method for forecasting the increased failure on the example of the fluid leakage in the pump injection unit is proposed. The permissible boundaries of the change in the relative force on the polished piston rod are drawn up. As a result, the failure increase is forecasted based on the frequency of the relative force on the polished piston rod getting within the interval obtained.

Исследование эффективности работы установок скважинных штанговых насосов с комбинированной стеклопластиковой штанговой колонной

Исследование эффективности работы установок скважинных штанговых насосов с комбинированной стеклопластиковой штанговой колонной

Position-Binary Technology for Processing the Signals of a Load for Identification of the Technical State of Deep-Well Sucker-Rod Pumps

A position-binary technology for processing the signals of a load caused by the weight of a rod string on the suspension of a sucker-rod pumping unit is proposed. The method may be employed for identification of the technical state of deep-well sucker-rod units. An algorithm for identification of the technical state of the unit is developed. An implementation of the new algorithm on an actual facility with the use of a remote system confirms the increased reliability of automated diagnostics.

Exploration and practice of integrated control technology for tubing and sucker rod lopsided wearing in directional well

Changqing oil field generally used sucker rod pump. In 2015, the maintenance operations reached 42 thousand times, the cost is about 550 million RMB, the work caused by tubing and sucker rod lopsided wearing accounts for 42.8% of the total. This paper focused on the main factor of lopsided wearing which caused high frequency of maintenance work, a three-dimensional mechanical simulation model of sucker rod string was established based on the analysis of borehole trajectory, rod mechanics; A model for calculation the neutral point of double material composite pipe and steel tubing is carried out; The calculation method of allowable stress is modified; at the same time, the application conditions of the mature process is standardized, to achieve the integration of technology management. The sucker rod lateral force dynamic distribution and allowable stress calculation method, the sucker rod parameter optimization and real-time warning, optimization of structure and the amount of wear resistant pipe string have been applied in oilfield. Compared with 2015, The number of maintenance operations decreased more than 6000 wells, operation frequency by 0.99 times / year - wells decreased to 0.85 times / year - wells, which is composed of 14 thousand and 500 well tube and rod failure wells decreased to 13 thousand and 300 wells, decreased 8%, annual cost savings of nearly 60 million RMB. It will have important guiding significance to prolong the pump checking period and cost control.

Model predictive automatic control of sucker rod pump system with simulation case study

This work enables accelerated fluid recovery in oil and gas reservoirs by automatically controlling fluid height and bottomhole pressure in wells. Several literature studies show significant increase in recovered oil by determining a target bottomhole pressure but rarely consider how to control to that value. This work enables those benefits by maintaining bottomhole pressure or fluid height. Moving Horizon Estimation (MHE) determines uncertain well parameters using only common surface measurements. A Model Predictive Controller (MPC) adjusts the stroking speed of a sucker rod pump to maintain fluid height. Pump boundary conditions are simulated with Mathematical Programs with Complementarity Constraints (MPCCs) and a nonlinear programming solver finds a solution in near real-time. A combined rod string, well, and reservoir model simulate dynamic well conditions, and are formulated for simultaneous optimization by large-scale solvers. MPC increases cumulative oil production vs. conventional pump off control by maintaining an optimal fluid level height.

An Improved Sucker Rod Pumping System Model and Swabbing Parameters Optimized Design

Considering the impact of fluid flowing into pump on sucker rod pumping system (SRPS) dynamic behaviors, an improved SRPS model with new boundary model is presented, which is a fluid-solid coupled model with the interactions among surface transmission, rod string longitudinal vibration, plunger motion, and fluid flow. A uniform algorithm is adopted instead of the mixed iteration algorithm for the surface transmission and downhole rod string vibration submodels, to reduce the difficulties of solving the entire SRPS model. The dynamic response comparison is executed between the improved model and the current model, and the results show that it will bring a calculation error on pump load and pump fullness if the progress of fluid flowing into the pump (PFFP) is ignored. Based on this improved model, a multitarget optimization model is proposed and the dynamic behavior of SRPS is improved with the optimized swabbing parameters.

Development of Prime Mover Loading on the Sucker Rod Lift During Coalbed Methane Production

A modern methodology has been proposed for the system design of prime mover loading in order to reduce the motor size and improve the efficiency of pumping system. Polished rod loading, plunger stroke length, gearbox torque loading and motor power are chosen as the basic design variables to implement the process of design calculation in producing coalbed methane (CBM) wells. Based on the kinematic and dynamic analysis of sucker rod pumping mechanism, the kinematic relations of polished rod loading are developed with the limits of specific CBM well conditions along rod string. The gearbox torque is determined by combining the counterbalance effect with the calculated dynamometer cards and torque factors. Then the design of prime mover is computed by combining the pumping speed with motor and drive efficiencies. The application characteristics of this method are demonstrated by the example of producing CBM wells in Ordos Basin. The interpretations of results show that compared with oil/gas fields, the load ratios of dynamic and friction to the total loads are relatively high and the computation of polished rod loads should involve the static loads as well as the dynamic and friction loads. The net gearbox torque is cyclic loading for the balanced operation. And the extreme value of net gearbox torque occurring on the upstroke is approximately equal to that on the downstroke. The maximum value of net gearbox torque is less than 50% of the peak value of unbalanced gearbox loadings. Moreover, the variation of instantaneous motor power versus crank angle is consistent with that of gearbox torque versus crank angle. The negative motor power results from the combination of the various moving components which drive the motor, exceed its synchronous speed and make the prime mover operate in a “regenerative power” mode. The value range of negative motor power is much smaller than that of unbalanced gearbox loadings. The result of this work is a mathematical model and a complex computer program used for the design calculation of prime mover loading in producing CBM wells. This makes it possible to maintain the gearbox torque in balance, load the prime mover more uniformly and provide a reasonable basis for the selection of pumping units.

Technology Update: Seismic Stimulation: An Eco-Friendly, Effective EOR Alternative

Technology Update Environmental and economic concerns have led to an increased interest in seismic stimulation as an alternative enhanced oil recovery (EOR) methodology. Seismic stimulation, achievable with the implementation of a single tool, requires significantly lower investments than gas, thermal, and chemical injection methods, while making minimal environmental impact. Applied Seismic Research (ASR), based in McKinney, Texas, has placed more than 200 of its proprietary seismic stimulation tools in more than 50 locations, including fields in Arkansas, California, Canada, Egypt, Kansas, Mexico, Oklahoma, Oman, and Texas. This article will examine the operation of the tool and highlight the EOR results achieved in a variety of formations. What is Seismic Stimulation? Seismic stimulation is the harnessing of low-frequency, high-energy elastic waves to mobilize oil. The method’s origins trace back to the 1950s when it was noticed that natural earthquakes could increase oil production by up to 45%. Attempts in the 1980s to duplicate earthquake effects by the use of surface vibrators above a targeted zone were largely unsuccessful and commercially unviable. Later development of tools that generate subsurface shockwaves proved more promising. ASR received the first patent for its technology in 2000. A “Greener” EOR Method In-situ seismic stimulation may be one of the greenest EOR options available. The method doesn’t involve injecting any amount of potentially harmful fluids or chemicals into the earth or dealing with the byproducts created by other EOR methods. In fact, it is implemented in a completely closed wellbore having no hydraulic communication with the formation. It can offer a measure of relief to field operators grappling with issues including managing groundwater contamination from harmful chemicals; dealing with the treatment, transport, and disposal of high volumes of contaminated wastewater; and/or handling the environmental consequences of the intense energy and carbon use occasioned by thermal injections. How the Tool Works The seismic stimulation tool (Fig. 1), which has a lifespan of up to 1.5 years and typically requires no maintenance, is powered by a conventional pumping unit and can be installed in abandoned wells at depths from 700 to 10,000 ft. It is relatively easy to transport to wellsites, coming in three preassembled segments in a single crate. The tool is installed into an abandoned wellbore, connected to a rod string and then to a pumping unit. The pumping unit drives movement of three plungers within the tool in unison. The lowest plunger contains a traveling valve to bring in fluids. When the plunger reaches the top of its stroke, it exits the lower barrel to release highly compressed fluids, creating the elastic waves.

ANALYSIS OF DAMAGE ROD STRING COMPONENTS IN SUCKER ROD PUMP IN THE FIELD SS

Field SS is a Heavy Oil field which means high viscosity oil making it difficult to flow. Therefore, artificial lift was used in this field to help lifting the high viscosity fluid, i.e. sucker rod pump (SRP). In the last several years, problem of the damage to the rod string was frequently occur. Rod string damage is usually indicated by the occurrence of broken or detached components. In order to overcome the damage of rod string components on the sucker rod pump, several parameters that causes rod string damage in 41 well samples in the field SS were analyzed and then recommendations were made as an alternative to minimize the occurrence of rod string damage. After analyzing the parameters that can cause rod string damage on 41 well samples in SS field, the cause of the breakdown of rod string is fluid pounding for 37 samples well, while the causes for 4 samples of other wells is not detected. After that, recommendation efforts is done, like size down pump speed and stroke length for 9 samples of wells, size down pump size and pump speed for 6 samples of wells and size down pump speed for 22 samples well. As for the undetected cause 4 samples of wells, is recommended to do proactive well service.

Improvement and research of the pump rod treaded connections

On the basis literary sources analysis, it was defined, that failures of the pump rod threaded connections are the most common exceed one-third of the total number of the rod string failures. It is due to non-uniform load distribution across thread turns of the pump rod threaded connections.
 The simulation modelling of standard design of pump rods was performed and graphic dependencies of stress distribution were developed on the gaps the pump rod threaded connections.
 The methods to reduce load non-uniformity across thread turns of the pump rod threaded connections were considered.
 The design of the pump rod connection was proposed; it shall have the variable mean diameter of the nipple thread by adding one more element, fitted in the nipple body hole. The comparison of stress distribution dependencies on the gaps the pump rod nipple of the standard and proposed design showed that stress decrease in the first gap of the thread turn by 60 MPa, and in the third and next turns stresses increases and become uniform by the value. This change of stresses on turn gap, when it is operated in the well.

Predicting Sucker-Rod Pumping Systems With Fourier Series

Summary The Fourier-series method (FSM) is used to solve the prediction problems of sucker-rod pumping systems. With the displacement and load at any point of the rod string, by means of FSM, the displacement and load at any other point of the rod string are obtained. With no need of pump models, FSM easily predicts various pumping conditions that are challenges to the conventional prediction methods. As for prediction, FSM is valuable to the design, selection, installation, and operation of sucker-rod pumping systems. As for diagnostics, the surface cards generated by FSM can be used as characteristic surface cards for diagnosis of the sucker-rod pumping systems in situations when only the surface cards are available. FSM is also a convenient method to generate surface cards for pump-diagnostic emulators in the laboratory environment.

The simulation model of sucker rod string transverse vibration under the space buckling deformation excitation and rod-tubing eccentric wear in vertical wells

Considering the limitations of the static buckling theory on the eccentric wear of sucker rod and tubing, a new dynamic analysis method for the transverse vibration of sucker rod in the tubing is proposed. Taking the axial distribution load at the rod body and the dynamic load at the bottom into account, the dynamic model of transverse vibration is established based on the space buckling configuration of rod string which regarded as the deformation excitation during the down stroke. To solve the mathematical equations, the finite difference method is used to discretize the well depth, and the Newmark-beta method is used to discretize the time. Meanwhile, a restitution coefficient is introduced to depict the change of velocity and the momentum after the collision. The result shows the phenomenon of rod-tubing collision occurs mainly in the down stroke after the rod string post buckling; the collision force from the wellhead to the bottom increases gradually, of which distributed almost along the entire well depth; and the high frequency collision occurs below the neutral point where the collision force is also the biggest. Further, the collision frequency and the collision force decrease successively from the neutral point to the wellhead direction. But during the up stroke, few collisions occur, and the collision force is also very small. The simulation model is suitable for the eccentric wear analysis of rod-tubing, and provides a new theoretical basis for the optimal allocation of the centralizer.

The numerical simulation of entire sucker rod string buckling with couplings in vertical wells

A new model is built to study the buckling of a rod string with couplings in the vertical well considering two important loads: the axial distribution load along the rod and the concentrated load at the bottom. Firstly, the calculation method for the axial distribution load of the sucker rod string is established based on a wave equation of longitudinal vibration. And, the simulation results show that the axial distribution load of sucker rod string has an obvious non-uniform distribution characteristic. The friction force between the plunger and the pump barrel (FFPPB), which is an important part of the concentrated load at the bottom, is improved based on both the Newtonian fluid (NF) and the non-Newtonian power law fluid (NNPLF) by using the Flunent software. In view of the above improvement of the computational method, a simulation model of the entire rod string buckling with couplings is established. Under the assumption that the coupling is taken as a radial constraint boundary, the two-point boundary value problem (BVP) algorithm is used to solve the differential equation, and the least square method is used to establish the continuity conditions on the supporting point of coupling. The simulation results show that the eccentric state of the plunger (eccentricity ratio $$\upvarepsilon =0\sim 1$$) has a significant influence on the eccentric wear area between the rod-tubings, which should be taken into account in the practical calculation. And compared without couplings, the contact pressure between the sucker rod string and the tubing is transferred to the couplings, which fits the engineering reality. Further, the simulation result implies the centralizers should be installed firstly near the couplings in order to protect the couplings better. The new method lays the theoretical foundation for the further studying the rod wear life and the design of the eccentric wear prevention.

Выбор конструкции утяжеленного низа колонны насосных штанг при добыче высоковязкой нефти

Выбор конструкции утяжеленного низа колонны насосных штанг при добыче высоковязкой нефти

A New Method of Force Calculation of Sucker Rod String in Directional Well

The actual wellbore trajectory of the directional well is an irregular spatial curve which is not only distorted, but also bended compared to the straight well. The complexity of the shape makes the sucker rod string in the work of a complex state of alternating stress, and withstanding axial compression, torsion and bending of the coupling effect. Meanwhile, the phenomenon of eccentric wear and disconnection of the sucker rod string becomes worse and worse. Based on the actual force of the sucker rod string in the directional well and the different force characteristics, a new method of force calculation of sucker rod string in direction well is given in this paper, the mechanics analysis models of the sucker rod string in three-dimensional directional well have been deduced respectively. Through the combination of mathematical geometry and traditional mechanics, the mathematical model can be used to obtain the analytic solution of the mechanical problem of sucker rod string, which is suitable for engineering design calculation and overall evaluation research.

Characteristic Analysis of longitudinal vibration Sucker Rod String With Variable Equivalent Stiffness

Considering the influence of variable equivalent stiffness on system response, the equivalent stiffness is defined as a step function, and a mathematical model of nonlinear longitudinal vibration of sucker rod string (SRS) is built. The dynamic response under displacement and load force excitation is solved by fourth-order Runge-Kutta method with zero initial condition. The results show the steady-state responses under the displacement and load force excitation of different function forms are different. The response curves of both displacement and velocity under the displacement and load force excitation of cosine function form have larger fluctuation than it under the displacement and load force excitation of sine function form. Therefore, the characteristic analysis of SRS plays an important role in understanding the influence of the excitation form and sensitive parameters on steady response.

Study on dynamic characteristics of hydraulic pumping unit on offshore platform

A new technology of offshore oil rod pumping production is developed for offshore heavy oil recovery. A new type of miniature hydraulic pumping unit with long-stroke, low pumping speed and compact structure is designed based on the spatial characteristics of offshore platforms. By combining the strengths of sinusoidal velocity curve and trapezoidal velocity curve, a kinematical model of the acceleration, the velocity and displacement of the pumping unit’s hanging point is established. The results show that the pumping unit has good kinematic characteristics of smooth motion and small dynamic load. The multi-degree-of-freedom dynamic model of the single-well pumping unit is established. The first and second order natural frequencies of the sucker rod string subsystem and the pumping unit subsystem are studied. The results show that the first and the second order natural frequencies among the pumping rod string, pumping unit-platform subsystem and the dynamic excitation have differences over 5 times from each other, indicating that resonance phenomenon will not appear during the operation and the dynamic requirements for field use are met in the system.

CONTROL DEPOSITS OF PARAFFIN, ASPHALT-RESIN COMPONENTS OF OIL

The current situation in the oil sector of Russia is characterized by a constant increase in the share of tight oil reserves, defined by low-permeability reservoirs and high viscosity. In addition, the production of oil and gas in most major fields is complicated by the removal of mechanical impurities, asphalt-resin-wax (ARW) and hydrate deposits as well as deposition of inorganic salts in wells. One of the most important problems in the oil industry is the deposition of paraffin deposits on the walls inner surfaces of tubings in the extraction and transportation of oil. AFS - natural composite material that consists of organic and mineral compounds. Deposits in their essence are represent «the greasy» suspension, or emulsion highly adhesive to various surfaces. The most important in the problem of these compounds formation is not the allocation of paraffins in the reservoir fluid flow but their deposition on the surface of process equipment. Moreover, for the paraffins to deposit on pipe wall the necessary condition is that temperature to be lower than that one of the liquid pumped. In the result of paraffin deposition inside the tubing the cross section of the pipe narrows, increasing the resistance to fluid flow and rod string displacement; the load on the head balancer SK increases, disturbing its balance and delivery rate decreases. All currently existing methods of dealing with AFS are mainly on non-regular basis allowing only to a certain extent to increase the turnaround time of the process equipment.

Interactive Web-Based 3D Wellbore Viewer Enables Collaborative Analysis

Summary Wellbore visualizations are often depicted by use of 2D perspective views. This approach is limited and potentially misleading. Of particular interest to rod-pumping and progressing-cavity pumps is the amount of side loading placed on the rod string throughout the wellbore. By illustrating the trajectory of a wellbore in 2D, some nuanced geometries can be easily lost. For example, a “corkscrew” wellbore, or any other complex wellbore geometry, can be very difficult to depict through simple perspective views. A corkscrew is best visualized at a specific camera angle where the shape is apparent. This best viewing angle is generally not at the simple 90° angle where typical 2D perspective views are generated. Distributed wellbore-visualization tools can be applied to both the design and analysis of pump installations. Interactive and shared views help to identify points in the well where problems may occur, or have occurred. Strategic placement of downhole equipment such as pump depth relative to perforations and historical fluid levels can be performed in a more intuitive way, taking into account a more accurate understanding of the geometry in a given well. The use of standards-based modern Web technologies enables the rapid deployment of such a tool to both desktop and mobile devices. The 3D graphics acceleration was previously only available in the Web browser through plugins and other third-party software installations. The 3D graphics can now be rendered natively in most modern Web browsers without the need for any additional software installation. Examples of such native visualizations can be found in Fig. 1.