Dynamic Fluid Level Research Articles

INVESTIGATION OF THE LOADS ON THE ROD PUMPING UNIT WHEN THE FLUID LEVEL IN THE WELL CHANGES

The balance of the pumpjack, which is the most common type of drive for downhole rod pumps, has a significant impact on the efficiency of pumping operation of the well. It determines the degree of loading of the pumpjack, the amount of electricity consumed. However, during the operation of the well, the balance of the drive may be disrupted due to a change in the load on the balancer head due to the weight of the liquid column in the annulus and acting on the pump plunger. This situation is noted for wells operating in the periodic pumping mode, as well as when the inflow of reservoir fluid changes for various reasons (unstable inflow, deterioration of permeability of the downhole zone of the formation, changes in reservoir pressure during development and other reasons). The paper considers the issues of forming loads on the drive of rod installations at a variable dynamic fluid level in the well. A mathematical model is presented describing the formation of loads on the head of the pumpjack balancer, taking into account possible fluctuations in the dynamic level. Verification of the proposed model was performed and a good agreement was obtained between the model and field dynamometer cards. A field example shows that a decrease in the dynamic liquid level causes an increase in maximum loads on the balancer head by more than 10 %. It was found that due to a change in the balance of loads on the drive, the torque on the crank shaft increases when the rods move upwards, which leads to an increase in the asymmetry of loads on the drive and a violation of the balance of the rocking machine. The relevance of the use of dynamic balancing systems is substantiated, which allow maintaining the balance of loads acting on the drive in changing external conditions.

A Wellbore Pressure Control Method for Two-Layer Coal Seam Gas Coproduction Wells

In coal seam gas (CSG) coproduction wells, due to the different production pressures of CSG production layer at different depths, the interlayer interference in wellbore seriously affects the gas production of a coproduction well. To effectively suppress the interlayer interference of the wellbore, a wellbore pressure distribution method for a two-layer coproduction well is proposed. Based on the analysis of the factors influencing the flow pressure distribution in the wellbore of two-layer coproduction wells, a method of coproduction flow pressure adjustment by regulating the wellhead pressure and the depth of the dynamic fluid level was established in this paper. The results show that wellhead pressure can directly affect the production pressure of two layers. The variation in layer 1 output mainly affects the pressure difference between the wellhead pressure and the pressure at the depth of layer 1, which has little effect on the pressure difference between layer 1 and 2. An increase in gas production from layer 2 would not only cause a pressure increase in layer 1, but also result in a reduction of the production pressure at layer 2. The maximum pressure gradient of the gas section is 0.14 MPa/100 m, and the pressure gradient of the gas–liquid section is 0.53–1.0 MPa/100 m.

Unveiling the Feasibility of Coalbed Methane Production Adjustment in Area L through Native Data Reproduction Technology: A Study

In the L Area, big data techniques are employed to manage the principal controlling factors of coalbed methane (CBM) production, thereby regulating single-well output. Nonetheless, conventional data cleansing and the use of arbitrary thresholds may result in an overemphasis on certain controlling factors, compromising the design and feasibility of optimization schemes. This study introduces a novel approach that leverages raw data without data cleaning and eschews artificial threshold setting for controlling factor identification. The methodology supplements previously overlooked controlling factors, proposing a more pragmatic CBM production adjustment scheme. In addition to the initial five controlling factors, this approach incorporates three additional ones, namely, dynamic fluid level state, drainage velocity, and fracturing displacement. This study presents a practical application case study of the proposed approach, demonstrating its ability to reduce reservoir damage during the coal fracturing process and enhance output through seal adjustments. Utilizing the full spectrum of original data and minimizing human intervention thresholds enriches the information available for model training, thereby facilitating the development of a more efficacious model.

Efficiency of an Inverted-Shroud Gravitational Gas Separator: Effect of the Liquid Viscosity and Inclination

Summary Gas-liquid separation is a typical process in many applications. For instance, gas separation is critical for the proper operation of electrical submergible pumps in the oil and gas industry as the pumps’ performance and lifetime are severely reduced when working with high gas/oil ratios. Gas-liquid separators are installed in oil production wells to reduce the void fraction at the pump inlet. The inverted-shroud gravitational separator stands out due to its efficiencies higher than 97%. This separator performs the gas separation process in two stages. The first is a segregation process related to inversion from liquid to gas continuous flow, whereas the second stage is related to gas entrainment associated with kinetic-energy dissipation process. The latter is more complex to model in the vertical than in the inclined separator’s position. Previous studies revealed that the liquid flow rate and separator’s inclination are relevant parameters for the gas separation efficiency (GSE). However, studies regarding the effect of the liquid viscosity on GSE are scanty. We evaluate the influence of the liquid viscosity and separator’s inclination on the GSE of an inverted-shroud separator (IS-separator) with water-air and oil-air mixtures. Efficiency maps for each inclination and empirical correlations to predict the GSE in the vertical inclination are proposed. New experimental data collected for several liquid flow rates and separator inclinations are offered in this study as a starting point to develop universal GSE maps. Different gas separation phenomena are observed depending on the flow pattern at the inner annular channel (IAC) of the separator and its inclination. The experiments conducted with the water-air mixture indicated turbulent flow, while the oil-air mixture revealed laminar flow for both inclined and vertical positions. The results suggest that the greater the liquid viscosity, the higher the GSE. The efficiency maps indicate that it is possible to reach total gas separation (TGS) for many experimental conditions. In practice, our approach proposes an alternative technology where the variables that influence the production well’s dynamic fluid level are actively controlled. Therefore, the IS-separator can operate under operational field conditions similar to those tested on a laboratory scale. This fact makes the IS-separator a promising tool for industrial applications.

Influence of formation drilling conditions on the choice of well stimulation method

The paper considers the influence of crank radius change on pumping unit kinematics during the dynamic fluid level control between tubing and casing in order to reduce the string fault rate. To improve the quality of prediction of these factors, the calculation of the movement of the polished rod over time is carried out using the Fourier variable separation method: the product of the balance bar head of a pumping unit defined as the movement of the slider of the pumping mechanism (in a straight line – like the chords of a circle), and the difference of such a chord with the length of the circle section equivalent to the movement of the articulated joint of the balance bar with the connecting rod. As a result, the accuracy of calculations is improved and the solution of the problem is simplified.

The research beam pumping unit of start-up mode

In the article, research of the beam-pumping unit start-up mode has been performed in accordance with the existing configurations of the rod column, the diameter of the plunger and the dynamic fluid level in the well. A mathematical model of the pumping unit actuator has been developed, it takes into account the mechanical characteristics of the drive motor, the moments of inertia of the belt drive and gears of the gearbox and the mass of the actuator components. Calculations have been performed for the variant of the pump rod column layout - two-stage, for the diameters of the plunger 55mm and depths of pump suspension of 1456 m. The problem of the beam-pumping units’ startup is defined for two cases. The first case is applied when the mass of the counterweights installed on the cranks of the pumping unit exceeds the mass of the column of rods and liquid, which is located in the tubing column above the plunger of the pump (rebalance of the beam pumping unit). The second - when the mass of counterweights is insufficient to balance the column of rods and the liquid in the tubing column above the pump plunger (imbalance of the beam pumping unit). The cases of rebalancing and imbalancing of the pumping unit occur in wells that are under periodic operative conditions. The first case - rebalancing occurs when the oil rocking pumping unit does not work, and the liquid level behind the tubing gradually increases up to its static level. After switching on the drive motor, the torque created by the crank counterweights exceeds the moment caused by means of the weight of the rod column and the liquid in the tubing column. Therefore, it is recommended to start the pumping unit from the lowest position of the rod suspender. In the second case, the imbalance occurs when the liquid’s dynamic level behind the tubing is lowered before receiving the submersible pump. Then the torque, created by the crank counterweights is insufficient to compensate the moment, caused by means of weight of the rods’ column and the liquid in the tubing column. Therefore, it is recommended to start the beam pumping unit from the top position of the rod suspension. As a result of calculations, the conditions of overload occurrence in wells with periodic operative conditions of the pumping unit are determined

Operational method for determining bottom hole pressure in mechanized oil producing wells, based on the application of multivariate regression analysis

One of the major tasks of monitoring production well operations is to determine bottom-hole flowing pressure. The overwhelming majority of wells in the Perm Krai are serviced using borehole pumps, which makes it difficult to take direct bottom-hole flowing pressure measurements. The bottomhole filtration pressure (BHFP) in these wells is very often determined by recalculating the parameters measured at the well mouth (annulus pressure, dynamic fluid level depth). The recalculation is done by procedures based on analytically determining the characteristics of the gas-liquid mixture in the wellbore, which is very inconsistent to perform due to the mixture's complex behavior. This article proposes an essentially different approach to BHFP measurements that relies on the mathematical processing of the findings of more than 4000 parallel mouth and deep investigations of the oil production wells of a large oil-production region. As a result, multivariate mathematical models are elaborated that allow reliably determining the BHFP of oil-production wells in operation.

Spatial structure and resource potential of heat storage in Nanmeng geothermal field

The geothermal conditions in Jizhong Depression are superior, and the area has many years of geothermal development history at present. Nanmeng geothermal field is located in the dominant area of geothermal resources in Jizhong depression, most of which is suitable for large-scale geothermal development. The main reservoirs in Nanmeng geothermal field include pore sandstone reservoirs of Neogene Guantao Formation and bedrock reservoirs of Jixian System. The Jixian System is the main thermal reservoir in the region, with a buried depth of 2000-4000 meters, a thickness of 500-700 meters, and a heat storage temperature of 70-105°C. It is characterized by large amount of water, good water quality and easy recharge of reservoirs. According to the difference of overlying strata structure, the buried depth of the main reservoirs in Nanmeng geothermal field gradually increases from south to north. In this paper, the annual geothermal recoverable resource of Nanmeng geothermal field is calculated as 0.3 × 1016J by the heat storage method, and the produced water temperature and the dynamic fluid level of the produced water are analyzed by the numerical simulation method. Finally, the most favorable well spacing of Nanmeng geothermal field is determined as 4A, which lays a foundation for the geothermal resource planning and development in Nanmeng.

Developing multilevel statistical models of determining bottom-hole flowing pressure in commercial oil well operations

One of the major tasks of monitoring oil production well operations is to determine bottom-hole flowing pressure (BHFP). The overwhelming majority of wells in the Perm krai are serviced using borehole pumps, which makes it difficult to take direct bottom-hole flowing pressure measurements. The BHFP in these wells is very often determined by recalculating the parameters measured at the well mouth (annulus pressure, dynamic fluid level depth). The recalculation is done by procedures based on analytically determining the characteristics of the gas-liquid mixture in the wellbore, which is very inconsistent to perform due to the mixture’s complex behavior. This article proposes an essentially different approach to BHFP measurements, that relies on the mathematical processing of the findings of more than 4000 parallel mouth and deep investigations of the oil production wells of a large oil-production region. As a result, multivariate mathematical models are elaborated that allow reliably determining the BHFP of oil-production wells in operation.

Study and Application of quickly putting into Production Technology without well killing in Shale Oil

Low-producing shale oil wells are put into production after reservoir modification. But the dynamic fluid level drops significantly in the initial stage, which result in a reduction in sand carrying capacity and a significant reduction in pumping efficiency. It also results in a significant shortening of the pumping inspection cycle. After the checking pump operation with conventional killing well, wells were found that the capacity recovery period was long. And the period of operating under pressure was long and costly. Checking pump cost increased significantly. Based on the situation of low-producing shale oil wells in the DA oilfield, by optimizing the downhole temporary plugging of the tubular column and simulating the timing of down pump, a quickly put into production technology of rod pump in shale oil is proposed. The technology can achieve downhole temporary plugging fast before checking pump, and lift out or lower pump without killing well. The field application shows that this technology can reduce the contamination of tight reservoirs result by killing fluid and significantly shorten the production recovery cycle.

Method for calculating dynamic loads and energy consumption of a sucker rod installation with an automatic balancing system

The efficiency of sucker rod pump installations, which have become widespread in mechanized lift practice, is largely determined by the balance of the drive. During the operation of sucker rod installations, the balance of loads acting on the rod string and the drive can change significantly due to changes in the dynamic fluid level, which leads to a decrease in balance and an increase in loads on the pumping equipment units. The increase and decrease in the dynamic level in accordance with the pumping and accumulation cycle occurs in wells operating in the periodic pumping mode. 
 It is shown that during the operation of equipment in a periodic mode, fluctuations in the dynamic level and, accordingly, in the loads acting on the nodes occur. This leads to the need for dynamic adjustment of the balancing weights to ensure the balance of the pumping unit. A system for automatic balancing of the rod drive has been developed, including a balancing counterweight, an electric motor that moves the load along the balance beam, a propeller and a computing unit.
 To study the effectiveness of the proposed device, a complex mathematical model of the joint operation of the reservoir - well - sucker rod pump - rod string – pumping unit has been developed. It is shown that due to the dynamic adjustment of the balance counterweight position, the automatic balancing system makes it possible to significantly reduce the amplitude value of the torque on the crank shaft (in comparison with the traditional rod installation) and provide a more uniform load of the electric motor. Equalization of torque and motor load reduces the power consumption of the unit.

A real-time diagnosis method of reservoir-wellbore-surface conditions in sucker-rod pump wells based on multidata combination analysis

This paper proposes a real-time diagnosis method that addresses the limitations of traditional “dynamometer cards” used for sucker-rod pump performance analysis. The “power vs. position plots” are proposed to demonstrate an improved diagnostic method for rod pump performance. On this basis, the working condition diagnosis plate of the sucker-rod pump well is created. The eigenvalues of dynamometer cards and “power vs. position plots” under different working conditions are extracted, and a combined diagnosis model based on feature recognition is established. The model not only diagnoses the wellbore condition but also the surface condition, which improves the diagnosis effect and expands the diagnosis range. In addition, considering the surface dynamometer card as the known condition, the one-dimensional damping wave equation is used to solve the downhole pump dynamometer card. By analyzing the change law of the pump-load slope-time relationship curve, the opening and closing points of the pump valve are accurately extracted, and the load difference between the upstroke and downstroke, and the effective stroke of the downhole pump dynamometer card are determined. On this basis, a calculation model of the dynamic fluid level and fluid production is established to determine the change in reservoir energy and analyze the supply and discharge relationship of the sucker-rod pump wells. Combined with the online collection of the surface dynamometer cards and “power vs. position plots,” the real-time diagnosis of oil well production systems can be realized. This can effectively improve the timeliness of sucker-rod pump performance analysis, reduce production management costs, and improve the production efficiency and benefits of the oilfield.

Optical Fiber-Based Level Sensor for High Temperature Applications

The novel optical fiber-based level sensing probe previously developed by Weathered was optimized to operate at higher temperatures and modified to measure local flow rates. The probe was submerged into a molten salt pool and a heating element run along the length of the probe was used to create a distinct temperature profile at the fluid-gas interface. An optical fiber was run in parallel which utilized optical frequency domain reflectometry to measure the temperature along the length of the probe at fine increments providing a quasi-continuous temperature profile. A numeric model was created in ANSYS to determine the optimal level sensor design. Three unique designs were then created and compared against one another to verify performance. A new level determining algorithm was generated in an attempt to increase the robustness of the sensor. With the optimal design and newly developed algorithm, the new level sensor was successfully tested up to 750 °C with an accuracy of ±1.5 mm and a response time of 3.0 ± 1.2 s and 7.5 ± 3.5 s for increasing and decreasing fluid levels, respectively. Additionally, the optimized level sensor was also tested under dynamic fluid level conditions to analyze the level sensors capability to measure fluid velocity. The velocity measurement capabilities were successfully tested in temperatures up to 750 °C with fluid velocities of 0.2 cm/s and 0.1 cm/s for increasing and decreasing fluid levels, respectively.

Numerical Simulation Research on Reflected Wave Characteristics of Oil and Gas Well Coupling

In order to analyse and identify the reflection morphology of the coupling reflected wave in the oil jacket annulus and to clarify the influences of different factors on the coupling reflection waveform, the COMSOL finite element analysis software is used to conduct a numerical simulation study on the above situation, and the response characteristics are obtained by calculation. In this paper, different signal sources are used to research the three-dimensional propagation characteristics of acoustic wave when it meets the coupling in the annular space. Numerical simulations are carried out for different coupling thicknesses, different coupling radii, and different oil casing annulus pressures to analyse their influences on the waveform of coupling wave. The results showed that when the polarity of the signal source was positive (negative), the coupling reflection signal was positive (negative) at first and then negative (positive). When the signal source is a positive-negative superimposed source, the first peak polarity of the coupling reflection signal is consistent with the signal source. The reflected signal is superimposed by the response generated by the positive and negative signal sources, respectively. With the increase of the coupling radius, the morphology of coupling wave remains unchanged while its reflected wave amplitude increases nonlinearly with the increase of the coupling radius; with the increase of the oil casing annulus pressure, the morphology of coupling wave does not change, but the amplitude of the reflected wave increases linearly with the increase of the pressure; as the thickness of the coupling increases, the peak-to-peak spacing of the coupling reflection wave becomes larger and the positive and negative peaks separate. The research results can provide theoretical basis and reference standards for the analysis of the characteristics of the signals received by the actual fluid level detector, the performance verification of the echo signal processing method and the correct identification of the dynamic fluid level position.

A model for calculating bottom-hole pressure from simple surface data in pumped wells

Bottom-hole flowing pressure and pump intake pressure (PIP) are important parameters to optimize the performance of oil wells. In recent years, downhole sensors are becoming widely used in electrical submersible pump systems to measure these pressures. However, it is still rare to use downhole sensors in sucker rod and progressive cavity pumped wells. In this study, two correlations were developed to calculate bottom-hole flowing pressure and PIP from readily available field data. The two correlations do not require measurements of buildup tests, but they rely on measuring the dynamic fluid level and estimating fluid gradient correction factor using either (1) the tubing gas flow rate or (2) the annular gas flow rate. Then, the PIP is calculated by the summation of either (1) the tubing pressure plus the tubing gaseous liquid column pressure or (2) the casing pressure, annular gas column pressure and the annular gaseous liquid column pressure. The correlations were developed using 419 field data points (389 points for training and 30 for testing) of wide range for each input parameter. Using the training data, the mean absolute percentage deviation (MAPD) between the calculated and measured PIPs is 25% and 20% for the first and second correlations, respectively. However, the testing data showed MAPD of 33% and 12% for the first and second correlations, respectively. The accuracy of these correlations is significantly higher than that of the previously available methods, and the correlations require simpler input. Such study is an original contribution to calculate the PIP with improved accuracy and without downhole pressures sensors.

Detection and Maintenance of Optimum Dynamic Fluid Level in Oil Well

This article discusses automation of oil wells equipped with sucker–rod pump assemblies. The control method of such assembly is proposed where variation of dynamic fluid level is selected as controllable parameter, the appropriate information can be obtained by mathematic processing of wattmeter graph signal. Simulation results are presented which confirm operability and efficiency of the proposed method of detection and maintenance of optimum dynamic fluid level.

The Monitoring System Design of Oil Well Dynamic Fluid Level

Dynamic fluid level is the most important indicator in the process of oil field development. By monitoring the dynamic fluid level of oil well, the working mode of pumping can be adjusted in time to maximize the utilization of resources. In this paper, a set of oil well dynamic liquid level monitoring system is introduced. The device collects sound wave data periodically and transmits data with the upper computer via WIFI and 4G to realize real-time monitoring of oil well dynamic liquid level. The monitoring software system of the upper computer is deployed on LAN and Aliyun server to realize remote users access to dynamic liquid level data in the oil field.

Geochemical response of produced water in the CBM well group with multiple coal seams and its geological significance-A case study of the Songhe well group in Western Guizhou

The geochemical response of produced water from coalbed methane (CBM) well group with multiple coal seams has rich geological significance. Taking 8 CBM wells of Songhe well group in western Guizhou as an example, the geochemical response characteristics and productivity significance of the CBM well group with multiple coal seams when inter-well interference or inter-layer interference appears have been examined mainly based on analyzing conventional ions, hydrogen and oxygen isotopes (δD and δ18O) of 7 batches of produced water samples in the stable production period of 1 year and 4 months, and dissolved inorganic carbon (DIC) stable isotopes (δ13CDIC) of 5 batches of produced water samples by cluster analysis and geological analysis methods. The study found that the change in dynamic fluid level has a good correlation with the Q-type clustering of δD-δ18O of produced water in the process of forming inter-well interference. With the formation of inter-well interference, the δD and δ18O clustering coefficient gradually decreases, and the fluids produced from the wells become more and more similar in property. In addition to the influence of drainage time, another main geological factor affecting inter-well interference is the buried depth of the coal seam. The larger the buried depth is, the larger the cumulative production of water, the faster the water circulation, the larger the Cl− concentration in produced water, the smaller the d-excess value (δD surplus index), and the smaller the cumulative production of CBM will be. In commingled CBM production of multiple coal seams, with larger span and multiple layers, inter-layer interference is likely to occur, resulting in unbalanced productivity contribution of the layers hard to tell. Because the δ13CDIC value in produced water from a well has a positive anomaly, the producing coal seams in the well are in the middle-upper layer of coal bearing strata; these coal seams have better permeability and higher water content, higher CO2 concentration and lower heavy hydrocarbon gas concentration offsetting each other, together with other geological conditions, it is concluded that the relatively large amount of CO2 formed by microbial reduction is the main cause of the positive δ13CDIC abnormality. Taking this well as the calibration well, combined with the Q-type clustering result of the δ13CDIC in produced water from the well group, considering the distribution of the developed coal seams and the change of the dynamical liquid level during the stable production period of the well group, the contribution of multi-coal layers in each well were estimated. If the cluster distance between the calibration well and another well is farther, the lower layer makes a larger contribution to the CBM productivity. If the cluster distance between the calibration well and another well is closer, the middle and upper layer contribute more to the CBM productivity, and it is mainly the production layers under the liquid level that produce CBM. This provides a unique hydrogeochemical analysis method for analyzing and identifying the contribution of production layers.

Алгоритм управления установкой штангового глубинного насоса для определения и поддержания оптимального динамического уровня жидкости в скважине

Алгоритм управления установкой штангового глубинного насоса для определения и поддержания оптимального динамического уровня жидкости в скважине

Model for Sucker-Rod Pumping Unit Operating Modes Analysis Based on SimMechanics Library

The article provides basic information about the process of a sucker-rod pumping unit (SRPU) model developing by means of SimMechanics library in the MATLAB Simulink environment. The model is designed for the development of a pump productivity optimal management algorithms, sensorless diagnostics of the plunger pump and pumpjack, acquisition of the dynamometer card and determination of a dynamic fluid level in the well, normalization of the faulty unit operation before troubleshooting is performed by staff as well as equilibrium ratio determining by energy indicators and outputting of manual balancing recommendations to achieve optimal power consumption efficiency. Particular attention is given to the application of various blocks from SimMechanics library to take into account the pumpjack construction principal characteristic and to obtain an adequate model. The article explains in depth the developed tools features for collecting and analysis of simulated mechanism data. The conclusions were drawn about practical implementation possibility of the SRPU modelling results and areas for further development of investigation.