Low Permeability Oilfield Research Articles

Analysis of Oil Displacement Effect of Ion Water Flooding Technology

The test area is a low porosity and low permeability reservoir. It was put into development in October 2005. The early effect was good, the later production decreased significantly, the ineffective water cycle was serious, the development layer series was few, and the main layer measures were difficult to increase production. In this paper, we carry out water quality analysis experiments of the produced fluid, and understood the change law of the main controlling factors Cl-and Ca2+ for evaluating the effect of ion water flooding. Combined with the production dynamics, we evaluated the effect of the measures, guided the optimization of the measures, designed the scheme, and understood the law of oil displacement. Through this study, it can be clearly and intuitively seen that the replacement effect of ion water flooding has a good oil washing effect, which has important application value and certain academic significance for the development of low permeability oil fields.

Dynamic variations of oil components and microbial communities during indigenous microbial stimulation pilot study in low-permeability reservoirs

Indigenous microbial stimulation is considered as a highly promising technology for enhanced oil recovery (EOR) of low-permeability reservoirs. In this paper, oil components and microbial communities of indigenous microorganisms before and after bio-stimulation in the largest low-permeability oil field of China were discussed. The results showed that Pseudomonas aeruginosa was dominant in the original samples, followed by some sulfate-reducing bacteria (SRB) and iron-reducing bacteria (IRB), such as Desulfovibrio oxyclinae, and Methylopila capsulata, Deferribacter abyssi. After bio-stimulation, the species of microorganisms gradually decreased, the content of Pseudomonas aeruginosa reached 2∼3 times than that of the original samples. The harmful bacteria, such as SRB and IRB, gradually disappeared. The Pr/Ph of the oil decreased, whereas the Pr/nC 17, Ph/nC 18, and ∑nC 21−/∑nC 22+ increased. The average molecular weight of oil decreased after the microorganisms were stimulated, in which the contents of N1-containing compounds increased, and that of O1-containing compounds decreased. The contents of biphenyls, naphthalene, and its derivatives decreased. Whereas those of aromatic compounds, such as phenanthrene, quaternary, fluorene, and their homologs increased. Pilot study was applied in LD field block, the average water cut of 27–47 well group decreased from 87.60% to 74.86%, the oil production increased from 12.18 t/d to 29.58 t/d.

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.

Study on Damage Mechanism of Waterflooding Development in Weizhou 11-4N Low-Permeability Oilfield

Weizhou 11-4N oilfield is a medium-low-porosity and low-permeability reservoir. The oilfield was initially developed by edge and bottom water energy and then transferred to water injection development. Affected by poor physical properties and heterogeneity of the reservoir, the oilfield appeared in the process of water injection development. When the water injection pressure increases, the water injection volume continues to decrease, and it is difficult to meet the injection requirements. On the basis of the analysis of reservoir heterogeneity, void structure, and clay minerals of reservoir, the water injection compatibility experiment, damage evaluation experiment, and nuclear magnetic resonance-velocity sensitivity experiments were carried out to clarify the damage in the process of oilfield water flooding development. Experiments show that the main causes of damage in Weizhou 11-4N oilfield water flooding development process are water quality incompatibility and strong velocity-sensitive damage. The determination of water type shows that the injected water and formation water are MgCl2 water type and NaHCO3 water type, respectively, under the classification of Surin water type, resulting in the formation of scale with calcium carbonate as the main component in the reservoir. Incompatibility of water quality is an important cause of reservoir damage and scaling. In the reservoir-sensitive flow experiment, the experimental core showed strong velocity sensitivity, the average velocity sensitivity damage rate was 466.31%, and the average critical velocity was 2.98 m/d. Nuclear magnetic resonance experiments show that the core has a significant decrease in average pore size after water flooding. The main damage range is the tiny throat of 0-2 μm. In this paper, the main damage interval of velocity-sensitive damage in the Weizhou 11-4N area and the change trend of void structure after velocity-sensitive experiment are clarified by nuclear magnetic resonance and velocity sensitivity experiments. The main cause of block reservoir damage provides the basis for the oilfield to take targeted measures and provides a guarantee for the efficient development of the subsequent oilfield.

Isolation and Characterization of Viscosity-Reducing and Biosurfactant-Producing Bacteria in Low-Permeability Reservoir

Microbialenhanced oil recovery has gained more attention in recent years due to its low cost and eco-friendliness. However, studies on the application of this technique in the low-permeability reservoirs are few. In this study, eight strains from the Ordos Basin low-permeability reservoir that produce biosurfactant and reduce viscosity were identified. Strains could produce biosurfactants (lipopeptide and glycolipids) to emulsify the oil and had good tolerance on temperature (25°C-50°C), salinity (1 g/L-50g/L), and pH (5-10). After the actions of A-3, SC4534(2), SC4561, and JSC4535, the content of long-chain n-alkanes were decreased by 51.2%, 28.3%, 35.2%, and 28.9%, respectively. The naphthalene in aromatic hydrocarbons was also effectively degraded by the strains that were screened, and the degradation rate was higher than 84%. Additionally, all strains were able to reduce oil viscosity, which was reduced by 27-51% (in seven days). 16S rRNA gene sequencing analysis indicated that seven strains belong to the genus Bacillus and one belongs to the genus Rhodospirillaceae. The results revealed that the existence of high-efficiency strains that can significantly improve the properties of crude oil in low-permeability oil fields though biodegradation and use of biosurfactants, which is of great significance for the application of MEOR in low-permeability oil fields.

Numerical Analysis of Dynamical Effects Associated with a Plugging String in a Horizontal Well

The finite element method has been applied to simulate the dynamics of a water plugging string in a complex horizontal well of a low-permeability oilfield. The force associated with the pipe string and the packer has been determined under the sucking action of the oil well pump. Such analysis has been conducted for a real drilling well, taking into account the process of lifting, lowering, unblocking and water plugging. Comparison between field measured data and simulation data indicates that the model is reliable and accurate. The packer creep effect under different pressure differences has also been investigated in the framework of the same model.

A Continuous-Time-Based MILP Model for Production and Transportation Scheduling in Nonpipelined Wells in Low-Permeability Oil Fields

Abstract The marginal wells in low-permeability oilfields are characterized by small storage size, scattered distribution, large regional span, low production, intermittent production, etc. The production mode of these wells is nonpipeline mode. In our previous work (Zhang et al., 2019), a novel mixed-integer linear programming (MILP) model using a discrete-time representation was presented for the operation scheduling of nonpipelined wells. However, too many discretization time points are required to ensure the accuracy of the model. Even for moderately sized problems, computationally intractable models can arise. The present paper describes a new continuous-time representation method to reformulate this schedule optimization problem. By introducing the continuous-time representation, the binary variables are largely reduced. The solution effect for different model sizes is also investigated. When the model size increases to a certain degree, a feasible solution cannot be obtained within a limited time. The results of a case study originated from a real oilfield in China show that the continuous-time model requires less time to obtain the optimal solution compared to the discrete-time model. In details, considering a same scale problem, the solution based on the continuous-time model saves 52.25% of the time comparing with the discrete-time model. The comparison validates the new model’s superiority.

Bio-inspired superhydrophobic interface of nano-gaseous film for reducing injection pressure in oil reservoirs

Superhydrophobic wettability inspired by the “lotus effect” is an intriguing property in nature, but it is rarely applied in oilfield development. Superhydrophobic nanomaterials can effectively solve the problem of “high injection pressure and insufficient water injection” in low permeability oilfields by changing the properties of the core surface, which is of great significance to the development of low permeability oilfields. Herein, we report a novel type of superhydrophobic nanoparticle (SHNP) simply modified by fluorinated long chains, and a stable nanofluid is successfully prepared by compounding surfactant. The prepared SHNP nanofluid has an excellent core drag reduction effect, and the drag reduction rate is 1.35 times that of conventional NPs under the same conditions. The SHNPs assemble on the core surface to form a large number of micro/nanorough structures, which can effectively reduce the surface roughness of the core. The PIV experimental results show that compared with the injection of pure water, the center flow velocity in the subsequent water flooding center increases by 98.27% after the injection of SHNPs nanofluid (the flow velocity decreases by 53.45% after the injection of NPs). Moreover, bubble probe AFM technology has successfully shown that bubbles can be captured through the SHNPs superhydrophobic interface to form a gaseous film. By using the barrier effect of the gaseous film, the liquid–solid interface is converted to a liquid–gas-solid interface, thereby reducing the large resistance caused by the direct contact between the liquid and solid. Such SHNPs with simple modification and low cost have broad application potential in oilfield development.

Study and Application of Ultrafine Temperature-Resistant and Salt-Tolerant Swellable Particles in Low Permeability Reservoirs

Based on the characteristics of low-permeability oil and gas reservoirs and the requirements for profile control and water plugging and for water cut decrease and production increase in the high water cut stage of the middle and late exploitation periods, ultrafine temperature-resistant and salt-tolerant swellable particles DS-1 suitable for low permeability oilfields were prepared by introducing N,N-dimethylacrylamide(DMAA) monomers into the 2-acrylamido-2-methylpropanesulfonic acid (AMPS)/acrylamide(AM)/N,N-dimethylbisacrylamide ternary crosslinking system. The median of initial particle size was 22.00 μm, and is compatible with formation pore throats. A static water absorption experiment showed that the particles can still maintain a high swelling ratio after 15 days at a high temperature and high mineralization degree, so they have long-term stability. The physical and chemical properties of the particles were analyzed microscopically using the infrared spectrum method and the scanning electron microscope (SEM) method. A dynamic displacement experiment confirmed that the particles can effectively plug dominant channels of waterflooding, increase the injection pressure, and improve the interlayer and intralayer heterogeneity. In the field experiment, the swellable particles DS-1 were used as a main slug for water plugging operations, and a good water cut decrease and oil production increase effect was obtained.

Progress and prospects of carbon dioxide capture, EOR-utilization and storage industrialization

Carbon dioxide capture, EOR-utilization and storage (CCUS-EOR) are the most practical and feasible large-scale carbon reduction technologies, and also the key technologies to greatly improve the recovery of low-permeability oil fields. This paper sorts out the main course of CCUS-EOR technological development abroad and its industrialization progress. The progress of CCUS-EOR technological research and field tests in China are summarized, the development status, problems and challenges of the entire industry chain of CO2 capture, transportation, oil displacement, and storage are analyzed. The results show a huge potential of the large-scale application of CCUS-EOR in China in terms of carbon emission reduction and oil production increase. At present, CCUS-EOR in China is in a critical stage of development, from field pilot tests to industrialization. Aiming at the feature of continental sedimentary oil and gas reservoirs in China, and giving full play to the advantages of the abundant reserves for CO2 flooding, huge underground storage space, surface infrastructure, and wide distribution of wellbore injection channels, by cooperating with carbon emission enterprises, critical technological research and demonstration project construction should be accelerated, including the capture of low-concentration CO2 at low-cost and on large-scale, supercritical CO2 long-distance transportation, greatly enhancing oil recovery and storage rate, and CO2 large-scale and safe storage. CCUS-EOR theoretical and technical standard system should be constructed for the whole industrial chain to support and promote the industrial scale application, leading the rapid and profitable development of CCUS-EOR emerging industrial chain with innovation.

Analysis and Prospect of Fracturing Technology in Low Permeability Oilfield

Analysis and Prospect of Fracturing Technology in Low Permeability Oilfield

Discussion on the Development and Research of Low Permeability Oilfield Geology

Discussion on the Development and Research of Low Permeability Oilfield Geology

Study on Fracture Development Characteristics of Low Permeability Oilfield and Its Influence on Horizontal Well Pattern Deployment

Study on Fracture Development Characteristics of Low Permeability Oilfield and Its Influence on Horizontal Well Pattern Deployment

Prediction of reservoir key parameters in ‘sweet spot’ on the basis of particle swarm optimization to TCN-LSTM network

In oil reservoirs, the sweet spot is found that the well could be positioned quickly and accurately, the drilling rate and the oil-gas production are increased, development cost is reduced. Among them, sorting, granularity and porosity are important factors to evaluate whether the exploration area is a sweet spot. A low permeability oil reservoir is taken as the research object, this paper mainly focuses on the prediction of the above evaluation parameters. In order to solve this problem, this paper proposed a new deep learning hybrid model. The model is constructed based on temporal convolutional network (TCN) and long short-term memory network (LSTM). Firstly, the influence of logging parameters on the prediction of evaluation indexes is analyzed. Secondly, the model is used to predict the screened sequence data. In the process of model construction, particle swarm optimization (PSO) is used to optimize the global hyperparameters, and finally the prediction model is obtained. The model is compared with TCN algorithm, traditional machine learning and empirical formula. This model improves the prediction accuracy of reservoir evaluation parameters in low permeability oilfield.

Study on wellbore annular sealing technology based on the influence of fracturing operation in low permeability oilfield

At present, the fracturing technology has been very mature and is widely used in oil and gas field production operation. However, the fracturing operation will cause periodic changes in wellbore internal pressure and generate alternating stress. Due to the material factors of casing and cement sheath, the deformation of the two is inconsistent after stress, and then the damage of cement sheath and the failure of wellbore annulus seal occur. After water injection development, it is easy to produce channeling risk, so the performance of cement sheath is crucial. In view of this problem, through the theoretical analysis, experimental analysis and organic combination analysis of wellbore annulus cement ring sealing, the critical failure threshold of wellbore annulus cement ring under fracturing operation is given, which provides certain guidance for improving wellbore annulus sealing and reducing the risk of channeling after fracturing operation in the future.

Study of single well pressurization and water injection experiments in low permeability reservoirs

In the process of water injection development in low-permeability and extra-low-permeability oil fields, the water absorption capacity of injection wells continues to decline, and the number of under-injection wells is increasing, which affects the development effect of oil fields. In this paper, we take X oilfield as an example and carry out single-well pressurized water injection tests to determine the range of reasonable injection pressure for pressurized water injection and the geological conditions suitable for pressurized water injection. Through this project research, the water absorption capacity of injection wells can be effectively improved, and the oilfield development effect is improved, which provides a new idea to solve the problem of water injection difficulties in low permeability oilfield.

High-Temperature-Resistant, Clean, and Environmental-Friendly Fracturing Fluid System and Performance Evaluation of Tight Sandstone.

Hydraulic fracturing, as an oil-water well stimulation and injection technology, is particularly important in the production and stimulation of low-permeability oil and gas fields, and the performance of the fracturing fluid directly affects the success of the fracturing operation. Compared with traditional water-based fracturing fluids, clean fracturing fluids have the advantages of strong sand-carrying ability and easy gel breaking with no residue. Aiming at the problem of poor temperature resistance and shear resistance of the clean fracturing fluid, based on previous research, this paper selects a high-temperature-resistant clean fracturing fluid system and evaluates the performance of the system. The research results show that the system has better rheological properties, better sand-carrying performance, shorter gel-breaking time, and less damage to the reservoir.

Study on Injection-Production Adjustment Technology in Sanduo Oilfield

On the basis of understanding the geological characteristics of low permeability oil fields with scattered sand bodies, this paper studies the water injection policy, response characteristics and the oil fields entering the middle water cut stage since the production. Affected by the scattered underground sand bodies, it is exposed to the influence of low water flooding control degree and less water flooding direction. After water breakthrough, it is difficult to adjust the water well scheme and the formation pressure level is low. In order to alleviate the above contradictions, oil wells are converted to injection, water drive control degree is improved, and formation energy is increased. In order to improve the control degree of sand bodies, several schemes are compared to find out the transfer injection mode suitable for oil fields with scattered sand bodies, increase the proportion of multiple connections and improve the oil recovery ratio.

The posibility analysis of high-pressure drilling in Block A in Field F

The drilling and shut-in regulations for peripheral oil fields currently follow the standard of the old area of placanticline, i.e., the wellhead pressure of water injection wells within 600m of the drilling well is reduced to below 3MPa before drilling. The regulations did not take into account the depth of the target formation, structural development, reservoir properties and oil and water well connectivity in the peripheral oilfield, which made it difficult to relieve pressure in most of the wells and resulted in longer drilling and shut-in cycles and greater impact on production. In order to minimize the impact of drilling and shut-in on field development and to explore drilling and shut-in limits and standards suitable for peripheral fields, drilling tests were conducted in Block A for infill wells. The feasibility of high pressure drilling in the peripheral low permeability oilfield was analyzed by analyzing the drilling site conditions, the quality of post-completion cementing and the logging data of the completed wells under different pressure conditions.

Analysis on the current situation of water injection development in a block of sunenoer Oilfield

Surennuoer oilfield is located in the north of Wuerxun Sag, beierhu depression, Haita basin. This paper introduces the geological characteristics of the oilfield from the aspects of oilfield structure and reservoir physical properties; On the basis of carefully combining the dynamic and static data, this paper analyzes the dynamic development characteristics of the oilfield since it was put into development. At the same time, combined with its characteristics, it summarizes the main understanding of the current oilfield development, which provides reference experience for the future water injection development adjustment of low permeability oilfields, and has certain reference significance for the efficient and rapid development of similar oilfields.