Oilfield Water Injection Research Articles

Analysis of Corrosion Causes and Optimization of Corrosion Evaluation Methods for Water Injection System in Changqing JY Oilfield

Abstract Based on the corrosion characteristics of the water injection system in Changqing Oilfield, an experimental study was conducted on the corrosion of the water injection system caused by carbon dioxide, hydrogen sulfide, bacteria, and water treatment agents in the produced liquid. The main influencing factors of corrosion in the water injection system were analyzed, and it was clarified that the corrosion of the water injection system in Changqing Oilfield was mainly caused by oxygen corrosion, which also had an impact on the water quality of the injection. Combining static corrosion analysis with the introduction of pitting and dynamic corrosion rate testing methods, the average corrosion rate of JY oilfield water injection system has a positive correlation with pitting corrosion, while the average corrosion rate of clean water has a stronger correlation with pitting corrosion. The corrosion evaluation method has been optimized, providing technical basis for formulating effective anti-corrosion measures for the oilfield.

Dilation Potential Analysis of Low-Permeability Sandstone Reservoir under Water Injection in the West Oilfield of the South China Sea

At present, many offshore oil fields are facing problems, such as pollution-induced near-well zone blockage, poor inter-well connectivity, and strong vertical heterogeneity, which lead to insufficient formation energy and low production in the middle and late stages of development. It is necessary to develop a new technology to overcome these issues. In this regard, water-injection-induced dilation technology, which was already proven to have positive effects on loose sandstone reservoirs, was controversially applied to an offshore low-permeability reservoir. To investigate whether the water-injection-induced dilation technology is suitable, experiments were conducted to analyze the dilation potential of offshore low-permeability sandstone reservoirs, namely, X-ray diffraction, laser particle size analysis, physical simulation, computed tomography scan, and electron microscope scanning experiments. The X-ray diffraction experiments showed that the samples had more than 80% non-clay mineral content and a high brittleness index, which meant more complex microfractures under water injection. Particle size analysis experiments revealed that the particle size was mainly between 10 μm and 100 μm, and thus belonged to coarse silty sand. According to the sorting grade, the sample particle size distribution was uniform and the reservoir was more prone to dilation. The true triaxial physical simulation showed that a volumetric dilation zone occurred around the wellbore, where complicated microfractures occurred. This paper provides adequate evidence and mechanisms of dilation potential for an offshore low-permeability sandstone reservoir.

Evaluation of the Development Effect of Oilfield Water Injection

Evaluation of the Development Effect of Oilfield Water Injection

Mixed transportation optimization model for oilfield water injection synergizing pipeline network and trucks

The water injection network is a common method in oil extraction processes, generally characterized by high energy consumption. Therefore, the adoption of scientifically sound and rational optimization schemes is crucial. However, due to the limited injection capacity of water injection station (WIS), when their supply is less than the demand of the injection wells, trucks are used for supplementary water injection. This paper introduces an oilfield water injection method under water injection pipeline and trucks coordination transport. An optimization model for oilfield water injection in this mixed transportation mode is established to address the supply-demand imbalance in the water injection network. The study uses a specific oilfield water injection system as a case study to validate the applicability of the mixed transportation water injection model (MTWI-Model) compared to the conventional water injection model (CWI-Model). The findings indicate that when only CWI-Model is used, the water volume from the injection station cannot meet the demands of the injection wells, leading to the cessation of some wells and potential overload of pumps in the station, thus affecting the normal operation of the water injection station and ultimately the oil recovery rate. Furthermore, the paper compares the optimization results of the mixed transportation model under two scenarios: fixed and non-fixed water intake points (namely MTWI-FP-Model and MTWI-NFP-Model). The results show that the mixed transportation mode with non-fixed water intake points is more economical, saving a daily cost of 632.28 Yuan/d compared to the fixed point scenario.

Design of water nozzle shape and structure optimization for eccentric injection mandrel in water injection wells

AbstractInjection mandrel is one of the key components to control the water injection rate of each layer in the layered injection process in the oilfield. The imbalance between the layers can be changed by an optimized injection mandrel to control the appropriate injection rate. This study introduces an approach to optimize water injection in oilfields, focusing on a new eccentric injection mandrel with adjustable flat nozzles. Firstly, computational fluid dynamics (CFD) simulations were carried out using FLUENT software to model and analyze the flow characteristics of the injection mandrel. The simulation results were validated through experimental comparisons, demonstrating excellent consistency. Secondly, the nozzle shapes were identified and optimized. The semicircle nozzle demonstrating superior regulation performance due to its smallest differential pressure and a robust linear relationship between flow rate and opening degree. Finally, orthogonal tests are designed for three influencing factors of the eccentric injection mandrel: number of injection holes, injection hole diameter, and nozzle shape. The simulation results show that the number of injection holes is 36, the diameter of injection holes is 3.2 mm, and the eccentric injection mandrel has relatively better performance. After optimization, the differential pressure between the inlet and outlet is reduced by 57.14%, and the average shear stress on the fluid is reduced by 3.88%. This innovative methodology, employing CFD simulations and orthogonal tests, offers precise water injection rate control, reducing water wastage, and optimizing energy consumption in water injection systems.

Application of Big Data Water Distribution Technology in T Block of Q Oilfield

With the extension of oilfield development time, a large amount of production data has been accumulated in the oilfield water injection development process, which brings great challenges and opportunities to the adjustment analysis, diagnosis, and optimization of oilfield development [1]. Based on geological static data, historical data such as production and monitoring at both ends of injection and production, and using big data and deep learning methods, this paper forms a big data analysis method for water injection optimization with the mode of “finding key layers of key wells, implementing key monitoring and deciding the best scheme”. Good results have been achieved in guiding the adjustment of single well water quantity in Block T of Q Oilfield. Eight water injection adjustment schemes have been deployed on-site, 16 intervals have been adjusted, and the daily water injection has been adjusted from 136 cubic meters to 120 cubic meters. After adjustment, the accumulated oil in the connected oil well stage has increased by 262.3 tons, and the production decline in the well area has been effectively controlled, which provides new technologies and new ideas for the dynamic development adjustment of the oilfield.

Study on the Effect of Surface Properties of Non-Metallic Materials on the Growth Mechanism of Crystallization Fouling

In order to alleviate the serious problem of scaling in oilfield water injection pipelines, we developed a scale collection device and applied it in the field based on the idea to “change passive descaling to active descaling”, but the effect is not stable, so we need to improve the descaling effect. Firstly, this paper analyzed the effect of surface physical properties of eight non-metallic materials on CaCO3 scale growth and their mechanisms through shear experiments. Then, the influence of surface properties (roughness, contact angle, surface energy) on the scale growth characteristics was investigated. Finally, the influence of material surface properties on the friction coefficient was studied by a cyclic experiment. The results showed that except for PTFE (polytetrafluoroethylene), the fouling amount of the other seven materials changed abruptly at 18 h, and the maximum fouling amount of FRP was 2.05 g/m3. It was found by scanning electron microscopy that the fouling particles on the surface of FRP were interconnected and presented in the form of flakes, which was related to the larger surface wettability, surface energy, and roughness. At the same time, the surface properties of the material have a certain relationship with the friction coefficient, and the influence of the contact angle on the friction coefficient is greater than the surface energy and roughness.

Hydrogeochemistry of productive Lower Jurassic deposits of the Talinskoye oil field in Western Siberia

The aim of the study is to determine, in terms of the prevalence of influence of natural or technogenic factors, the factors of formation of the hydrogeochemical composition of productive Lower Jurassic deposits of the Talinskoye oil field. During the study, the authors of the article evaluated the effects of sedimentogenesis, elutriation, neotectonic processes and oilfield water injection on the chemical composition of the waters studied. Water injection is known to cause changes in the hydrogeochemical balance and the formation of technogenic hydrogeological systems. Formation water salinities currently range from 3.7 to 15.3 g/dm3. More than 8960.3 thou-sand m3 of water was injected from overlying sediments into productive formations to maintain reservoir pressure (2014-2021). The authors analysed the genetic coefficients of different types of water (including injected water). Then they compared the coefficients. It was concluded that injected water currently doesn't have a significant impact on the hydrogeochemical appearance of the productive Lower Jurassic reservoirs of the Talinskoye oil field.

Study of cyclic waterflooding for improving oil recovery in Lukeqin heavy oil reservoir

Long term water injection in Lukeqin heavy oil field results in a rapid increase of water cut. It is an urgent need to conduct a study on the influencing factors of heavy oil waterflooding. Experiments are used to conduct the effect of heavy oil viscosity change law on the development. Numerical simulation is used to analyze the viscosity and rhythmic conditions to clarify the production mechanism of waterflooding in heavy oil reservoirs. The feasibility study of cyclic water injection in heavy oil reservoirs is analyzed because water channeling is serious in continuous water injection, while cyclic waterflooding can slow down the injection water surge. To begin with, when using the improved cyclic waterflooding method, the working mode, reasonable number of cycles and the timing of cyclic waterflooding need to be optimized to obtain the optimal combination injection scheme. Furthermore, to investigate the mechanism of oil increase by cyclic waterfiooding, different production wells were divided into the channeling well, the seepage channel well and the normal wells according to the streamline strength, and then analyzed the mechanism influencing factor such as pressure difference and capillary force to study when cyclic waterflooding for the three types of production wells. Pressure differential are the most effective in increasing oil in the normal well, followed by the seepage channel well, and channeling well. The capillary force have the best water control effect on the channeling well, followed by the seepage channel well and the normal well. The capillary force play a dominant role in the well water control in the channeling well. The effect of increasing oil in the normal well is dominated by pressure difference. Well pressure difference and the capillary force have little to no dominant effect on the seepage channel well. The results demonstrate that cyclic waterflooding can effectively improve the recovery rate of three types of wells, with the degree of improvement from good to bad, in the order of the normal well, the channeling well and the seepage channel well. The novelty of this work lies in the combination of experimental and numerical models (mechanistic and practical) and simulation studies using three different types of wells, thus analyzing the mechanistic influence of pressure differential and capillary forces in it and concluding the dominant mechanism of action - the mechanism of development of heavy oil cyclic waterflooding is the effect of pressure difference control on production increase and capillary force control on reducing water cut.

Identification of Water Flooding Advantage Seepage Channels Based on Meta-Learning

As the water injection oilfield enters into the high water cut stage, a large number of water flooding advantage seepage channels are formed in the local reservoir dynamically changing with the water injection process, which seriously affects the water injection development effect. In oilfield production, water injection and fluid production profile test data are direct evidence to identify advantage seepage channels. In recent years, some scholars have carried out research related to the identification of advantage seepage channels based on machine learning methods; however, the insufficient profile test data limit the quantity and quality of learning samples, leading to problems such as low prediction accuracy of learning models. Therefore, the author proposes a new method of advantage seepage channel identification based on meta-learning techniques, using the MAML algorithm to optimize the neural network model so that the model can still perform well in the face of training tasks with low data sample size and low data quality. Finally, the model was applied to the actual blocks in the field to identify the advantage seepage channels, and the identification results were basically consistent with the tracer monitoring results, which confirmed the feasibility of the method. It provides a new solution idea for the task of identifying advantage seepage channels and other tasks with low data quality, which has a certain guiding significance.

Study on the influence of oilfield water injection on casing damage

The casing damage of oil and water wells has seriously affected the normal production of the oilfield. This paper analyzes the high occurrence of casing damage in Saertu oil layer, and finds that there is a contradiction between the water injection production of the wells in Saertu formation and the prevention and control of casing damage. Although the wellhead oil pressure can be guaranteed to be lower than its fracture pressure during production, the injected energy at the wellhead includes pressure potential energy and kinetic energy. Because the fracture pressure of Saertu formation is relatively low, the total injected energy is often higher than its fracture pressure, resulting in water injection at an excess fracture pressure. Unreasonable water injection will lead to the destruction of the underground rock stratum, which acts on the casing and forms casing damage.

Mechanism of Nano-depressurization and Injection-Augmenting Technology and Its Application in China’s Oilfields: Recent Advances and Perspectives

In China, most oilfields have entered the late stage of water injection development. Considering that the injected water quality has not reached the standard for a long time, the formation of organic and inorganic scale blockage has become increasingly serious, resulting in a continuous increase of injection pressure in water injection wells. The difficulty of water injection and low recovery ratio have mainly limited oilfield development. Considering the small size, large specific surface area, and other excellent properties of nanoparticles, they can easily enter the pore channel without reducing the permeability and damaging the formation, thus attracting extensive research attention at home and abroad. This work reviews the mechanism of depressurization and injection-augmenting and the application of nanomaterials in China’s oilfields. The future development prospects are also forecast. The mechanism of nano-depressurization and injection-augmentation mainly includes the following: (1) viscosity reduction, scale inhibition, and removal of wax and colloidal asphalt deposition; (2) inhibition of hydration and swelling of clay minerals; (3) change in the wettability and enlargement of the water flow path; (4) hydrophobicity of the nanoadsorption layer and drag reduction by water flow sliding; and (5) micro–nano double hydrophobic and self-cleaning effects. Through the strong chemical adsorption force between nanoparticles and the rock surface, the wettability of rock is changed by expelling the water film, and the permeability of the reservoir is improved by the sliding effect and the mechanism of preventing clay swelling. Nano-depressurization and injection-augmenting technology has been applied in China’s oilfields for many years, and studies have mainly summarized field tests in the past 10 years. The construction blocks include some typical middle–low-permeability reservoirs, such as the Bohai, Changqing, Daqing, and Jianghan Oilfields. Nano-depressurization and injection-augmenting technology has achieved obvious results, biological nanomaterials have obvious advantages over chemical additives, and its characteristics of environmental friendliness and long validity provide a new research direction for oilfield water injection and oil recovery, with broad development prospects.

Balance and Correlation Analysis of Oilfield Injection-Production System Based on Data Mining

Appropriate water injection volume is the most basic parameter required to maintain stable formation pressure and ensure the development effect of water flooding in oilfields. However, the determination of appropriate water injection volume has always been a major problem in oilfield water injection management. Based on the Grey relational algorithm, this paper determines the optimal connected injection-production well group through the study of the dynamic relationship between oil and water wells. To specifically predict water injection, a Sparrow search algorithm optimisation model based on Sine mapping is proposed. A Sine-SSA-BP algorithm was devised to predict water injection volume and both the improved algorithm and the original BP algorithm were applied to real-world data to assess their predictive accuracy. The prediction results of the Sine-SSA-BP algorithm were found to be closer to the true value than the results of the original BP algorithm, and the average error percentage is reduced by 23.86%. Therefore, the new algorithm can predict and calculate the water injection volume more accurately. The research content of this paper can provide a theoretical basis for advising adjustment measures in the block to slow down the rise of water content, maintain stable production, and improve the efficiency of the mechanical mining system.

A new oilfield injection water quality decision-making method

Due to long-term water injection development, the formation permeability will continue to decline. The water injection quality selected before the water injection development cannot always meet the water injection demand of the reservoir permeability. In order to reduce the damage of the water injection water quality to the reservoir, it is necessary to re-select the appropriate water injection water quality. This article proposes a water quality decision-making method considering the history of water injection. According to SY/T 5329-2012 standard for water quality, water quality sensitivity coefficients are given for reservoirs with different permeability under five different injection water qualities. The sensitivity of water quality was characterized qualitatively and intervals of water quality sensitivity coefficients were determined. Adjust the water quality of the injection based on the consideration of water injection history on permeability injury. After a simulation study it was found that changing the water quality of the injection water could increase the recovery rate by 1.6%. The method is of great significance for the old oilfield water quality and water injection efficiency improvement.

Sequential field development plan through robust optimization coupling with CNN and LSTM-based proxy models

Well operation optimization is vital in maximizing the net present value (NPV) of the field development plan (FDP). As well operation is a time-series scenario, this problem contains numerous parameters to be optimized and countless solutions. This results in huge optimization time to evaluate each scenario using the reservoir simulator, especially with robust optimization. In this study, particle swarm optimization is coupled with the deep learning-based proxy model to solve such problems in the 2D synthetic and 3D Egg cases. First, the long short-term memory (LSTM) proxy model is developed to estimate the reservoir response to the well operation scenario instead of reservoir simulation. When the drilling and bottomhole pressure (BHP) schedules are entered into the input layer for the proxy model, the average cumulative field oil and water productions and field water injection from the multiple reservoir models are obtained in the output layer. In case of well pattern, the optimized scenario of the location and type of wells in Kim et al. (2021a) was fixed in this study. After the LSTM proxy model fits with the training data pair of time-series BHP schedule and corresponding the responses obtained by ECLIPSE (ECL), it can predict the time-series field response for given BHP scenario. When the calculated NPV from the LSTM is compared with the true NPV from ECL, the coefficient of determination for the validation and test datasets is higher than 0.97, solving the overfitting problem of the simple neural network (NN) proxy model. It is critical to select a proper deep learning algorithm according to the characteristics of the input and output data. While the convolutional NN (CNN) is proper to make a proxy model for well pattern scenario, which consists of the static images with the same dimension in Kim et al. (2021a), the LSTM is suitable for well operation scenario, which changes over time. Second, the drilling and BHP schedules are optimized under the constraint of the maximum available rig. Also, to reduce these high-dimensional optimization variables, we define the BHP schedule as a cosine function instead of the stepwise approach. It reduces the number of training data required for the proxy model. Third, optimization strategies are reviewed for both the well pattern and well operation. The sequential proxy, CNN-LSTM, shows similar NPVs with the results of the sequential ECL-ECL. However, CNN-LSTM requires only 12% of optimization time compared to ECL-ECL for the 3D case. Therefore, CNN-LSTM is proposed as the reasonable solution for reliable decision-making for the FDP in a short time.

Three-dimensional interwell electromagnetic detection

Electromagnetic methods play an important role in the exploration and development of oil and gas resources and metal minerals. The ground electromagnetic method is largely limited by the detection depth and resolution in actual work. In order to improve the detection accuracy and working efficiency of interwell electromagnetic detection, this paper proposes a three-dimensional inter-well electromagnetic detection method. The method utilises one or more production wells in the production well pattern to construct a transmission galvanic couple source, which effectively reduces the shielding effect of the metal casing on the transmission signal in the well and improves the transmission signal power. The downhole and the ground receiving arrays were used for simultaneous observation, with high observation network density and detection accuracy. With pseudo-random multi-frequency signals as excitation, the working efficiency of the electromagnetic detection is significantly improved. The downhole receiving array makes the measuring electrode closer to the target geological body, increasing the response signal intensity of the anomalous body. Meanwhile, the impact of electromagnetic interference on the ground is effectively reduced, and the detection depth is increased. The ground receiving array is composed of multiple measurements points located on concentric circular measuring lines, which is beneficial for the identification of the azimuth and angle information of underground geological targets. A detection model for anomalous bodies with different parameters in the formation was established. Numerical results show that for anomalous bodies with different resistivities in the formation, the electric field response curves on the ground and the downhole receiving arrays are significantly different. Because the emission source is located on the symmetry axis of the model, the excited field is distributed axisymmetrically. The ground observation response can effectively identify anomalous bodies with different azimuths and electrical parameters in the formation. The downhole observation response is sensitive to the upper and lower interfaces of the abnormal body, and the depth information of the abnormal body can be accurately determined. The calculation results of the oilfield water injection dynamic monitoring model show that the electric field response curves on the ground receiving arrays of different measuring lines can effectively reflect the water injection process of the underground reservoir, including the direction of water penetration and the change in reservoir resistivity. The research results show that this method can better identify the resistivity characteristics, azimuth information, and depth information of anomalous downhole bodies, while effectively delineating the reservoir boundary and revealing reservoir changes. This provides a theoretical basis and technical ideas for the three-dimensional electromagnetic detection of complex interwell geological bodies.

Analysis on causes and countermeasures of abnormal water injection in oilfield Wells

In the process of oilfield development, water injection is a very important work content, and the reservoir exploitation quality, efficiency, are closely related. Oilfield water injection technology has been widely applied and popularized, but in the process of specific application, it will also have some influence on the oilfield, such as causing oil layer blockage. The author will focus on the application of oilfield well water injection, analyze the related reasons for the occurrence of anomalies, and put forward solutions to the abnormal phenomena one by one, so as to ensure that the relevant personnel can solve the related problems quickly when applying this technology, and achieve stable oilfield production.

A Method for Optimising Pump Configuration and Operation in Oilfield Water Injection Network

Some oilfields in China encounter operating problems on water injection pipeline networks. Due to the unreasonable planning of the pipeline, water cannot be transported to the end of the pipeline and injected into the wells. Also, a large amount of water is repeated transported. This paper aims to deal with the above issues by proposing a method of using pipeline pumps to pressurise the water injection pipeline network, which can improve the water supply capacity of the pipeline network, and reduce the energy consumption of water injection. The pipeline pump has the characteristics of convenient installation, compact structure, and wide application range. To effectively utilise the pipeline pump in the water injection network, a pipeline pump boosting optimisation model is developed, taking the lowest cost of the pump and operating energy consumption of the water injection system as the objective function, and considering the constraints of water injection, pipeline network hydraulics and pump operation. An oilfield in China is studied as an example, the results show that the proposed model can optimise the pump installation position and operations. The operating cost was reduced by 184 k CNY, and the total annual cost was saved by 154 k CNY. The maximum water injection increment can reach 4,700 m3/d, which improves the water supply capacity of the water injection pipe network, and the needs of oilfield water injection planning can be satisfied.

In-depth isolation of highly permeable zones for reservoir conformance control

In-depth isolation of flooded-out reservoir zones is widely used in water injection and water production control in oilfields. This paper looks at the research results of a new technological solution – a method and mechanism of deep-penetrating insulation of highly permeable reservoir areas. Approximate mathematical models are used to describe oil-saturated reservoirs flooding with chemical compositions used as a displaced fluid. The mathematical model of the problem is reduced to a partial differential equation with initial boundary conditions. The article also presents the results of the numerical implementation of the transfer equations of concentrations of gel-forming components and a thickener. In a non-uniform grid domain, the problem at hand is replaced by a discrete problem using a combination of an explicit and implicit-difference scheme that increases the order of accuracy and is solved by the run-through method. Effective algorithms for solving the one-dimensional problem are obtained, taking into account the equations of adsorption and convective diffusion. The developed method increases the efficiency of the in-deep isolation treatment of flushed zones and can be applied to related reservoir flooding projects.

Research and practice on optimal design method of the oilfield water injection system pipeline network

The efficiency of oilfield water injection system is generally low and energy consumption is high. With the deepening of oilfield exploitation, the water cut of the oilfield is increasing, the power consumption of the water injection system is increasing year by year, the oilfield exploitation cost is increasing, and energy conservation and consumption reduction are very important. In order to improve oilfield water injection efficiency and reduce water injection energy loss, this paper puts forward the pipe network optimization design method of partial pressure water injection, establishes the mathematical model of partial pressure water injection pipe network and throttling loss calculation model, compiles the calculation software of partial pressure water injection mathematical model, optimizes the partial pressure interval, calculates the partial pressure points, effectively reduces the energy loss of water injection system and improves the efficiency of water injection system.