Separate Layer Water Injection Research Articles

Application of separate layer water injection in high differential pressure wells

With the development of a heavy fine-RRB-layering system and dynamic adjustment, the number of large differential pressure wells increases gradually. The effect of high-pressure difference wells on water injection development is that it is difficult to separate water injection allocation, low pass rate of layers and short effective period of separate sealing, which affects the development effect of water flooding. For this reason, the research on stratified water injection technology with large pressure differences is carried out using step-by-step throttling. The throttling pressure difference borne by the water nozzle is reduced. The large throttling pressure difference produced by the water nozzle is realized. The qualified rate of the layer section is increased to improve the anti-creep performance of the expansion Packer and the sealing effect of large pressure difference injection wells and to extend the service life of the Packer. The field application results of 216 wells in the Shengli Oil Field show that the technique can effectively improve the pass rate of the layers and the sealing effect of the layers and prolong the life of the string.

Research and implementation of encoding and decoding technology of Layered Water Injection Based on Wave Code

The layered water injection technology based on wave code communication is one of the fourth-generation separated layer water injection technology, widely used in low permeability oil field with pressure operation injection Wells, has the advantages of simple operation and low cost. However, there is a problem of low communication efficiency. In order to solve the problem of low communication efficiency, this paper compares the advantages and disadvantages of amplitude time modulation encoding and pulse position interval encoding, and proposes a method based on pulse position interval encoding and decoding. Finally, the pressure wave communication experiment is carried out. The results show that when the pulse width is set to 5s, the communication time of a set of opening instructions is only 3 minutes, which greatly improves the communication efficiency of the wave coding process. The research on encoding and decoding can provide technical and theoretical support for improving the communication efficiency of layered water injection based on wave code.

Production characteristics and displacement mechanisms of infilling polymer-surfactant-preformed particle gel flooding in post-polymer flooding reservoirs: A review of practice in Ng3 block of Gudao Oilfield

The pilot test of infilling polymer-surfactant-preformed particle gel (PPG) flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China. However, the production characteristics and displacement mechanisms are still unclear, which restricts its further popularization and application. Aiming at this problem, this paper firstly analyzes the production performance of the pilot test and proposed four response types according to the change of water cut curves, including W-type, U-type, V-type response, and no response. Furthermore, the underlying reasons of these four types are analyzed from the aspects of seepage resistance and sweep efficiency. The overall sweep efficiency of gradual-rising W-type, gradual-decreasing W-type, and early V-type response increases from 0.81 to 0.93, 0.55 to 0.89, and 0.94 to 1, respectively. And the sum of seepage resistance along the connection line between production well and injection well for U-type and delayed V-type response increases from 0.0994 to 0.2425, and 0.0677 to 0.1654, respectively. Then, the remaining oil distribution after polymer flooding is summarized into four types on the basis of production and geological characteristics, namely disconnected remaining oil, streamline unswept remaining oil, rhythm remaining oil, and interlayer-controlled remaining oil. Furthermore, the main displacement mechanisms for each type are clarified based on the dimensionless seepage resistance and water absorption profile. Generally, improving connectivity by well pattern infilling is the most important for producing disconnected remaining oil. The synergistic effect of well pattern infilling and polymer-surfactant-PPG flooding increases the dimensionless seepage resistance of water channeling regions and forces the subsequent injected water to turn to regions with streamline unswept remaining oil. The improvement of the water absorption profile by polymer-surfactant-PPG flooding and separated layer water injection contributes to displacing rhythm remaining oil and interlayer-controlled remaining oil. Finally, the paper analyzes the relationships between the remaining oil distribution after polymer flooding and production characteristics of infilling polymer-surfactant-PPG flooding. The study helps to deepen the understanding of infilling polymer-surfactant-PPG flooding and has reference significance for more commercial implementations in the future.

A pressure pulse recognition method based on flow-adaptive double threshold for pressure pulse telemetry

Pressure pulse telemetry as a novel and effective method of communication has received more and more attention in the field of separate layer water injection for the intelligent oilfield, and identification of the effective pulses and their positions is one of the key technologies. For the logging while drilling process, the fixed threshold method is widely used to identify the pressure pulse. However, in the process of water injection, the amplitude of pressure pulse changes with the change of flowrate controlled by process, which will lead to low recognition rate of traditional fixed threshold pressure pulse. Therefore, a pressure pulse recognition method based on flow-adaptive double threshold with fixed time window is proposed. The packet length of instructions and responses is designed to be short and fixed in order to reduce communication time and failure cost, and the fixed time window method is adopted to improve the decoding efficiency of for a frame of data. The pressure pulse recognition method based on flow-adaptive double threshold is used to identify the effective pulses and their positions to adapt to the change of pressure pulse amplitude induced by different flowrates. The first threshold which is set to fixed and lower than the pulse peak with minimum possible flowrate, is used to filter the most of noise and catch the effective pulses with little noise pulses. The second threshold which is adaptive to changes of the flowrates, is determined by average of three maximum peaks of caught pulses from the first threshold, and is used to identify the effective pulses and their positions. In the experimental well with 2000 m deep, the test results show that the error rate of pulse recognition reduce to 0.003% and communication success rate significantly increase from 50% to more than 96.5%. It means that the proposed double threshold method can be adaptive to identify effective pressure pulse under different flowrates, and then can significantly reduce the error rate of pulse recognition and improve two-way communication performance between the wellhead controller and downhole distributors.

Field Test and Discussion on Individualized Test Cycle of Water Injection Wells

As the oilfield enters the late development stage of ultra-high water cut, the number of separate layer water injection wells increases year by year, and the single well interval becomes finer and finer, which makes the test adjustment more difficult and the qualification rate of periodic test matching lower, and finally affects the decline of water injection qualification rate. In view of the above reasons, it is urgent to formulate a personalized test cycle. It is a major task to ensure the stable production of the oilfield to ensure the water injection, enough water injection, improve the quality of water injection, and ensure that the water drive oilfield development meets the program requirements at the injection end. In the past year, the influencing factors of water injection qualification rate of water drive separate layer wells have been analyzed, and the change law of inspection qualification rate has been explored. Through the demonstration of experimental work, the personalized test cycle is discussed. The original 4-month test cycle is shortened to 2 months, and the test cycle is extended for wells with 100% qualified rate, and the test cycle is shortened for wells with less than 80% qualified rate. The problems such as long inspection period, low qualified rate of water injection and difficult single well test and adjustment are solved. To achieve accurate water injection, and ultimately achieve the purpose of stabilizing oil and controlling water.

Research on optimization of single well testing workload and efficiency

With the enlargement of production scale and the increase of survey and adjustment work, the mismatch between test requirement and test capability becomes more and more serious. In order to further control the test cost and improve the efficiency of survey and adjustment, according to the characteristics of the peripheral oil reservoirs and sections, differential management of survey and adjustment cycle and effective methods of matching injection points are actively carried out, on the basis of satisfying the development requirements and smooth operation of various indexes, solve the mismatch between test requirements and test capabilities. By analyzing the use cycle of test data under different conditions, the type of wells with extended use cycle is determined, which can effectively reduce the need of test work under the condition that the separate layer water injection is qualified. The distribution rules of different sizes of nozzles are statistically analyzed, and the selection rules of nozzles in special layers are made clear in advance to improve the debugging efficiency of injection allocation point.

Effect evaluation and influencing factors of stratified water injection in low permeability reservoir

The main production layers in Danba oil area of Yanchang oilfield are Chang 4 + 5 and Chang 6 oil layers, which are the main development areas for increasing reserves and production. In view of the unclear influencing factors of water injection effect and the disunity of effect evaluation in the study area, the stratified water injection effect evaluation and influencing factors of low permeability reservoir are studied by means of production data statistical analysis and numerical simulation. The results show that the effect of water injection in the study area is affected by five factors: intraformational heterogeneity, interlayer heterogeneity, interlayer pressure difference, fracture and water injection timing, the results show that the water injection effect is obvious in the study area by using the five indexes of water drive reserves producing degree, water storage rate, water drive index, oil recovery rate and water drive control degree. The research results provide ideas for the study of high-efficiency separate layer water injection in low permeability reservoir, and provide guidance for the next step of potential mining.

Study on Reasonable Injection-Production Parameters of Water-Flooding Reservoir: A Case Study of Daqing Oilfield

This paper, by conducting comprehensive analysis on water-flooding reservoir, intensively studied and discussed the characteristics of geological development, determined the evaluation indexes of development effect, carried out research from five steps, the first is the introduction part, it conducted indepth study and discussion from research background, research significance, literature review, and research methods four aspects. The second outlined the related theory from the optimization principle and mechanism of injection-production parameters, and the distribution mechanism of remaining oil two aspects. The third analyzed the current situation of reasonable injection-production of water-flooding reservoirs in Daqing Oilfield from reservoir characteristics and reservoir deposition. The fourth evaluated the water-flooding development effect from combined water cut, changing conditions of production and predicted recovery ratio. The fifth intensively studied the reasonable injection-production parameters of water- flooding reservoirs in Daqing oilfield from design of separated layer water injection plan, maintaining level reservoir formation pressure, and reasonable plan of injection-production ratio and oil recovery rate three aspects, and provides theoretical guidance for later targeted excavation of water-flooding reservoirs.

Achievements and future work of oil and gas production engineering of CNPC

Abstract This paper summarizes the latest achievements and technological progress in oil and gas production engineering of China National Petroleum Corporation (CNPC) and discusses the main four challenges faced: developing low quality resource at low oil price; keeping stable production of mature oilfields when well oil production drops year by year; low systematic efficiency, high cost, prominent environmental protection issue and short of technological strategy for high water cut ratio and high oil recovery ratio oilfields; and lacking of high level horizontal well drilling and completion technology to develop unconventional and deep reservoirs. Three technological development directions to address these challenges are put forward: developing fracture controlling stimulation and well factory to produce low quality resource economically, developing re-fracturing technology for old wells in mature oilfields, promoting the fourth generation separate layer water injection technology to stabilize the production of mature oilfields; innovating new technologies of water flooding with nano-material, injecting and producing through one well.

Connotation, application and prospect of the fourth-generation separated layer water injection technology

Abstract The fourth-generation separated layer water injection technology was studied aiming at problems existing in current separated layer water-flooding technologies and production requirements. This paper discussed the connotation, core tool and key technologies, analyzed field application and prospected further development. The connotation is to realize digital real-time monitoring on single-well separated layer pressure and injection rate of injectors, network informationization of injection performance monitoring of blocks and reservoirs, and integrated reservoir and production engineering by combining injection program design and optimization with real-time adjustment of down hole separated layer water injection. An integrated water distributor, a core tool for this technology, and some key technologies including interval flow rate detection and injection allocation adjustment were developed. Moreover, this new technology was piloted in blocks and achieved expected results. In order to meet production requirements, it is necessary to keep research on key technologies, such as downhole interval flow rate detection, wellbore wireless communication, downhole self-power generation and vulnerable components fishing. In addition, this technology shall be properly combined with reservoir engineering, thereby developing a systematical and complete fourth-generation separated layer water injection technology that can underpin water flooding development sustainably.

Vibration wave downhole communication technique

Abstract To overcome the disadvantages of traditional downhole communication methods, a vibration wave downhole communication technique is proposed, and a vibration wave downhole communication system is developed. This technique has been verified by field test and is applied to separated layer water injection. It is shown by theoretical and test research that transmission of the vibration wave through tubing and casing appears as the alternate distribution of pass-band and stop-band. According to that, a multi-baseband transmission strategy is formulated. The on-off keying modulation and Manchester encoding scheme are used to load the control information into the vibration wave. A generation system of vibration signals is developed to realize the controllable conversion from electric energy into vibration wave energy. A receiving and decoding system of vibration waves, which uses a micro-vibration acceleration sensor as the signal pickup element, is developed too. A test system for vibration wave downhole remote transmission is designed and applied to field test. The feasibility of the technique and the accuracy and reliability of communication system are verified and the attenuation characteristics of casing vibration wave signals are obtained. This technique has been applied to separated layer water injection successfully with wide application prospect in wellbore control field.

A new concentric zonal water injection technique for highly-deviated wells

Abstract Existing eccentric zonal water injection techniques cannot meet the requirements of separated layer water injection, testing and adjustment in highly-deviated wells, because of their low fishing success rate of down-hole nozzles, low efficiency of connection between instruments and nozzles, and low precision of zonal flow rate test. A new concentric zonal water injection technique is proposed for highly-deviated wells. This technique adopts concentric testing and adjustment, i.e., the test instrument is concentrically connected with the down-hole regulator, with high success rate of connection. The down-hole regulator uses bridge-type channel to effectively eliminate inter-layer interference and thereby improving testing and adjustment efficiency. Water flow rate is adjusted with an eccentric valve, which features small loss in full-off state, small adjustment torque and easier water adjustment. This technique is functional for both collected flow test and non-collected flow test, so it is workable for low flow rate test. It can achieve packer seal test on line by cable, the status of seal balls can be monitored and all seal test operations can be completed in one trip. This technique can obtain flow rate, pressure, temperature and other parameters of any layer on line and automatic testing and adjustment of injection allocation rate, without fishing, significantly improving testing and adjustment efficiency. Until now, this technique has been tested in 11 wells (maximum well deviation of 55°), with tested flow rate error of less than 5%, and three-layer seal check and adjustment time of less than one day. Compared with the existing techniques, this new technique has advantages such as high testing and adjustment efficiency, high precision and low cost.

Evaluating Efficacy of the Separate Layer Water Injection of the Wells by Using Fuzzy Comprehensive Evaluation Method

It can directly reflect the effect of injection wells before and after the layering water injection by evaluating the layering water injection wells. In view of the uncertainties on the impact of various factors of injection well group, it can establish a series of quantitative method which is suitable for the evaluation of well group. Prior to the evaluation of water injection wells group, it is necessary to make evaluation of the existing wells. This study uses the fuzzy comprehensive evaluation method to calculate comprehensive evaluation coefficient of well group to judge the nature of each well group. According to the calculation of the comprehensive evaluation coefficient of E2 which is combined with the actual geological and development condition of Ba fault block 17, it can not only find the increasing relation between E2 values and water injection effect, but also evaluate the effect of water injection well group, which can determine whether symmetry layering water injection is reasonable or not. Key words: Layering water injection; Quantitative methods; Evaluation; Nature factor; Fuzzy comprehensive evaluation Key words: Layering water injection; Quantitative methods; Evaluation; Nature factor; Fuzzy comprehensive evaluation

Research on Injection Rate Allocation Fault Diagnosis in Integrated Separate Layer Water Injection Technology

Integrated separate layer water injection technology is an effective approach to reduce the workload of injection oilfield. The primary equipment which consists of flowmeter, motor and control value is placed underground for a long time. Injection rate allocation fault diagnosis is a problem with character of multiformity. The fault symptoms and reasons are random, and it is hard to differentiate them. Weighted fuzzy C-means clustering algorithm combining symptoms signals and fuzzy mathematics approach is used on the technology. The algorithm is based on fuzzy C-means clustering algorithm, and increase weight to each fault sample to reduce the impact of samples on fault classifications. Simulation and analysis illustrates that the algorithm is able to reflect the real structure of the sample data. And it improves the accuracy of fault classification.

Study on the Determination of the Separated Layer Water Injection Based on the Grey Synthetic Degree

The determination of the rational layered water injection intensity is the basis to stable oil production and high-yield in oil field. This article analyzes the various influential factors of the separated layer water injection intensity, using grey synthetic degree to determine the dominant influential factors. The weight value is obtained by normalization, each influence factor is quantization. Using grey correlation analysis method to determine the plane dividing coefficient and the vertical dividing coefficient, a reasonable stratified water injection intensity formula is got. This method considers the impact of these factors which consist of permeability, the measure transformation coefficient, perforation thickness, injector producer distance, location coefficient and the number of injector and producer. The problem which the contradiction exists in the same layer or between the layer and layer is obvious in the D block through combining with the current water injection development, reasonable dividing coefficient of block is established, a reasonable stratified water injection intensity formula is got, making well block reasonable injection and increasing adjustment effect of water flooding.

Dynamic tracking model for the reservoir water flooding of a separated layer water injection based on a well temperature log

A dynamic tracking model for the reservoir water flooding of a separated layer water injection was established. Based on the basic principles of heat and mass transfer, the water profile was determined using a well temperature curve. The Poisson process analysis and stochastic process methods were applied to calculate the water saturation, water breakthrough time, and water cut of each layer in a water-flooded reservoir at any given time. When the oil reservoir was producing water, the water cut predicted by the models, with consideration of the micro-pore distribution, approximated the practical measurement, having an error of less than 5 %. The sample application clearly indicated that larger water injection intensity (water intake per unit thickness) could result in more drastic water saturation variation, earlier water breakthrough, and faster increase in the water cut for layers with numerous high-permeability channels, such as fractures.

Current status and trend of separated layer water flooding in China

Abstract Separated layer water injection is one of the crucial means to keep long-term high and stable production of oilfield. “Bridge eccentricity + steel cable measuring and adjustment” has come into being as the principal water flooding technology, which, with improving adaptability, can meet the need of conventional water injection wells. As the water flooding fields enter high water-cut period, sand control for water injectors, separated layer flowrate test at low injection rate, high pressure and high temperature water injection, separated layer water injection for high-inclination wells and separated layer water injection monitoring and control will be the developing trend, directing water flooding towards automatization, intelligence and integration to meet the requirements of water injection under different reservoir and well type conditions for the purpose of ensuring efficient oil field development. Currently periodic progress have been made in downhole wireless communication, flowrate monitoring, nozzle dynamic adjustment, etc, forming the theoretical basis for automatic water flooding.

Applying Analytic Hierarchy Process to Determine Separate Layer Water Injection Rate of Single Well

The separate layer water injection rate determines the result of water injection. In the past, in order to inject a proper amount of water into different intervals, most of the time people would rely on their experiences. By employing this method, the amount of work was enormous and the result was not necessarily accurate. In this paper, five factors that would affect the water injection rate are taken into consideration, such as, thickness of the main well, the connected thickness, permeability, number of connected wells and oil saturation. A method of determining the proper water injection rate of single wells based on analytic hierarchy process is proposed. This method has been proven to be simple and accurate, the test result of a mathematical model also shows it fits the requirements of the oil field exploitation with current water cut and it is of great value to practical applications.

Study on the Determination of Separated Layer Water Injection Based on Grey Correlation Analysis Method

How to determine the separated layer water injection is a problem which reservoir engineers concern in flood development oil field. These various influential factors of dividing coefficient method are analyzed in this study. Grey correlation analysis method is used to determine the dominant influential factors. And the weight of different dominant influential factors is determined, which realizes the quantitative comparison among them in dividing coefficient formula. This method considers the impact of these factors which are consist of the measure transformation coefficient, perforation thickness, injector producer distance, location coefficient and the number of injector and producer. The separated layer water injection formula is determined. The scientific and reasonable injection allocation is realized. The problem which the contradiction exists in the same layer or between the layer and the layer is obvious in the S block through combining with the current water injection development. The separated layer water injection method is proposed necessarily. The formula for water injection is determined by grey correlation analysis method in Block S. These factors considered are more with the actual situation. And the reasonable injection allocation is realized. It is directive and referenced for other oil field or block.

Identification-Free Adaptive Separate Layer Water Injection Control Based on Expert Amendment

An identification-free adaptive control strategy based on expert amendment is proposed in this paper to solve the problem that it is difficult to establish mathematical model of water injection regulating process due to large time delay, strong nonlinearity and time variation in the flow control of separate layer water injection technology. In this control strategy, according to the past and current process information of water injection, the system output and trend can be estimated based on expert rules to amend the output of the identification-free adaptive control. The simulation result shows that this control strategy has perfect control performance and strong adaptability and it provides a feasible means for improving water injection effect.