Proppant Conductivity Research Articles

New model to evaluate the impact of quartz sand crushing on fracture conductivity in a proppant monolayer

The formation of a complex fracture network with sufficient proppant conductivity is crucial for the efficient development of deep shale gas. Due to cost considerations, quartz sand has commonly replaced ceramic proppant in the field. However, the significant crushing of quartz sand and its distribution as multiple particle sizes both before and after crushing, termed as particle size redistribution, raises concerns about its ability to meet the demands of the fracture network. Based on contact mechanics, we developed an evolutionary equation for fracture width that considers particle size redistribution. The particle crushing is described using a fragmentation replacement method, and changes in specific surface area before and after crushing are used to correct the permeability model of the fracture. By integrating models of fracture width and permeability evolution, we have established an analytical model for proppant conductivity that accounts for quartz sand crushing and its particle size redistribution. Numerical simulations further validate the predictive accuracy of our model. Sensitivity analyses investigate the impact of quartz sand degree of crushing, compressive strength, particle size, particle combination ratio, and closure pressure on fracture conductivity, demonstrating the reliability of quartz sand as a substitute for ceramic proppant in deep shale applications.

Investigation into the Variation Law of Network Fracture Conductivity in Unconventional Oil and Gas Reservoirs

The network fracturing technique is a key technology for increasing effective reservoir volume and enhancing production in shale oil and gas. The fracture network’s conductivity is one of the crucial factors affecting the efficient development of shale gas. To evaluate the variation patterns and influencing factors of the conductivity of network fractures, this study employed a proppant conductivity evaluation system and an equivalent theory testing method. It investigated the conductivity of propped and self-propped fractures under different angles and numbers of fractures. Experimental results showed that fractures with proppant support had higher conductivity than unsupported fractures. Smaller angles between secondary and main fractures resulted in greater conductivity. The conductivity of multi-fracture structures increased with the number of fractures. Under low-closure pressure conditions, self-propped fractures exhibited significantly higher conductivity than propped fractures, but this trend reversed under high closure pressure. This experimental research provides guidance for constructing network fractures with high conductivity in unconventional oil and gas reservoir fracturing.

Numerical Calculation and Application for Crushing Rate and Fracture Conductivity of Combined Proppants

Proppant is one of the key materials for hydraulic fracturing. For special situations, such as middle-deep reservoirs and closure pressures ranging from 40 MPa to 60 MPa, using a single proppant cannot solve the contradiction between performance, which means crushing rate and fracture conductivity, and cost. However, using combined proppants is an economically effective method for hydraulic fracturing of such special reservoirs. Firstly, for different types, particle sizes, and proportions of combined proppants, various contact relationships between proppant particles are considered. The random phenomenon of proppant particle arrangement is described using the Monte Carlo method, and the deterministic phenomenon of proppant particles is processed using an optimization model, achieving computer simulation of the microscopic arrangement of proppant particles. Secondly, a mathematical model for the force analysis of combined proppant particles is established, and an improved singular value decomposition method is used for numerical solution. A computational model for the crushing rate and fracture conductivity of combined proppants is proposed. Thirdly, the numerical calculation results are compared and discussed with the test values, verifying the accuracy of the computational model. Finally, the application of combined proppants is discussed, and a model for optimizing the proportion of combined proppants is proposed. The onsite construction technology is introduced, and the cost and economic benefits of combined proppants are compared with those of all ceramic particles and excessive all-quartz sand. It is proved that combined proppants can balance performance and price, and are an economically effective method for hydraulic fracturing of special reservoirs. The research results can select the optimal proppant material and optimize the combination of different proppant types, which can help achieve cost reduction and efficiency increase in oil and gas development.

Rod-Shaped Proppant Conductivity of a Hydraulic Fracture Considering Elastic-Plastic Deformation and Embedment: An Analytical Model

Rod-Shaped Proppant Conductivity of a Hydraulic Fracture Considering Elastic-Plastic Deformation and Embedment: An Analytical Model

Computer 3D Simulation of Proppant Particles

Proppants are one of the key materials for hydraulic fracturing, whose main role is to support fractures and create a channel through which oil and gas can flow. The nature of proppants is the most talked about feature besides their cost, for example, their sphericity, turbidity, particle size, or strength. The porosity, permeability, and fracture conductivity of proppants in fractures are also the main indicators to measure the performance of them. These indicators are usually obtained through physical experiments. However, experimental results often differ depending on the experimental scheme. Different stacking methods of proppant particles lead to this phenomenon. The nature of proppant particles in fractures varies with the way they accumulate. This paper will start with the microscopic arrangement of proppant particles. Considering the randomness and certainty of three-dimensional particle stacking and arrangement, the Monte Carlo stochastic method and an optimization model were used to conduct three-dimensional computer simulation of proppant particles. This lays an important foundation for revealing the randomness and regularity of the micro arrangement of proppant particles.

Feasibility of Proppant Flowback Control by Use of Resin-coated Proppant

Proppant flowback is a problem in Xinjiang oilfield. It decreases production rate of a fractured oil well, corrodes surface and downhole facilities and increases production costs. Curable resin-coated sand is a common technique to control proppant flowback. This article presents an experimental investigation whether it is feasible to control proppant flowback by use of resin-coated sand and whether resin-coated sand has a negative effect on proppant pack conductivity. It included two kinds of experiments, Proppant flowback experiment measured critical flow rate while the Proppant pack conductivity one measured proppant conductivity. The experimental results of proppant flowback show that the critical flow rate of resin-coated sand is far greater than that of common sand which means proppant flowback would not happen by resin-coated sand tail-in. Compared to Xinjiang sand conductivity, resin-coated sand conductivity is far smaller though it declines slightly which means use of resin-coated sand would lead to conductivity loss and sequentially results in production impairment. Experimental results show that it is feasible to control proppant flowback by use of resin-coated sand and resin-coated sand would affect fracture conductivity of a fractured oil well. Based on the experimental results, resin-coated proppant conductivity can be improved by use of resin-coated ceramic or liquid-resin-coated proppant. The achievements can give a direction towards how to select a resin-coated proppant and how to improve resin-coated proppant.

Simulation of proppant conductivity test: effect of particle size dispersion

A conductivity test of proppant material consists in confining a sample of the granulate at high pressure and then set a flow through the pack. The proppant particle size is the main variable controlling conductivity, but also particle size dispersion is considered important. Even though several studies consider mixtures of proppants of different meshes, there are not clear evidences as to whether the changes in conductivity with respect to a monosized proppant are caused by the mix itself or by the overall change in mean particle size. Hence, we use numerical simulations to answer the question: Does particle size dispersion significantly affects the proppant conductivity if mean particle size is kept the same? We measure conductivity and permeability by simulating (via a coupled Computational Fluid Dynamics–Discrete Element Method) the flow of water through binary granular packs. We find that size dispersion does not affect conductivity (in the dispersion range explored) if the mean particle size is conserved. However, we observe that in a binary mixture the large particles are subjected to larger stresses than in a monosized system, which makes them prone to crushing.

Study on the conductivity of proppant in shale reservoir

At present, in the process of developing shale reservoirs by hydraulic fracturing, proppants play a critical role in the overall fracturing effect. Therefore, accurately evaluating the conductivity of different proppants determines the development effect of shale reservoirs. In this paper, proppant screening is first carried out, and the conductivity of four different proppants under laying concentration and closing pressure is studied, including 10-20 mesh quartz sand proppants with non-standard particle size, and the influence of different factors on the embedding degree is analyzed. It is concluded that the bearing capacity of ceramsite proppant is usually 2-3 times stronger than that of quartz sand. The larger the particle size of quartz sand proppant is and the higher the concentration of sand is, the stronger the conductivity is. When the closed pressure of large-size quartz sand is less than 30 MPa, the laying concentration of 14 kg/m2 can obtain higher conductivity, and when it is greater than 30 MPa, 12 kg/m2 is more suitable for field application. The ceramsite proppant has been on the rise with the increase of closing pressure and sand concentration. The embedding depth gradually increases with the increase of closing pressure and the decrease of sand concentration. The embedding depth of shale is greater than that of sandstone, and the flow conductivity of proppant is usually lower than that of sandstone. According to the experimental results, large-size quartz sand has strong conductivity, but it is not easy to migrate and has poor bearing capacity. Therefore, large-size quartz sand proppant can be used in the low-pressure part near the well, supplemented by small-size quartz sand (40-70 mesh) to obtain better fracturing results. This study provides some technical guidance for shale reservoir development and shale fracturing dessert identification.

Evaluation of sintered bauxite proppant for binary enhanced geothermal systems

Solid granular proppant particles are widely used in oil and gas development to sustain permeability through fractures after hydraulic stimulation. Similar proppants are of interest for geothermal applications where the goal of sustaining permeability is the same, but the harsh geothermal environment risks rapid proppant degradation that will reduce fracture permeability. Here, we present proppant conductivity experiments using saw cut granite, tensile fractured granite, and aluminum control specimens packed with sintered bauxite ceramic proppants at concentrations of 0.0, 0.1, and 1.0 kg/m2. Simulated geothermal conditions included temperatures up to 130 °C and normal closure stresses up to 60 MPa. Compared to unpropped specimens, peak fracture conductivity enhancement was up to 6 orders of magnitude. At simulated geothermal conditions, proppants were able to sustain fracture conductivity over 60 h, but chemical dissolution and decreasing permeability over time were evident. Irreversible conductivity reductions with crushing and embedment of proppants during loading stages were also observed. Overall, sintered bauxite proppant remains a promising option for low-temperature binary-cycle enhanced geothermal systems.

An Experimental Study on the Impact of the Particle Size and Proportion of Composite Proppant on the Conductivity of Propped Fractures in Coalbed Methane Reservoirs following Pulverized Coal Fines Infiltration

Coalbed methane reservoirs exhibit a low strength and high heterogeneity, rendering them susceptible to coal fines generation during hydraulic fracturing operations. The detrimental impact of coal fines on the conductivity of the propped fracture has been overlooked, leading to a substantial negative effect on the later-stage recovery of coalbed methane reservoirs. Moreover, the particle size distribution of the composite proppant also affects the conductivity of the propped fracture. To mitigate the damage caused by coal fines to the conductivity of the proppant pack in CBM reservoirs, this study conducted conductivity tests on actual coal rock fractures. The aim was to assess the effect of various particle size ratios in composite proppant blends on the conductivity of complex fractures in CBM reservoirs. The ultimate goal was to identify an optimized proppant blending approach that is suitable for hydraulic fracturing in coal seams. The results indicated that, in terms of the short-term conductivity of coalbed methane reservoirs, the conductivity of composite proppants is primarily influenced by the proportion of large or small particles. A higher proportion of large particles corresponds to a stronger conductivity (e.g., the conductivity is highest at a particle ratio of 5:1:1 for large, medium, and small particles). On the other hand, a higher proportion of small particles leads to a poorer conductivity (the conductivity is lowest when the particle ratio is 1:1:5). In the long-term conductivity of coalbed methane reservoirs, the fluid flushing of the fracture surfaces generates coal fines, and small particles can fill the gaps between larger particles, hindering the infiltration of coal fines. Therefore, it is important to control the particle size ratio of composite proppants, with a predominant proportion of larger particles. This approach can maintain long-term conductivity and prevent the excessive infiltration of coal fines, thereby avoiding fracture blockage (e.g., the conductivity is highest at a particle ratio of 5:1:5, followed by a ratio of 3:1:3). Furthermore, considering the influence of proppant placement methods and the support effect on near-wellbore opening fractures and far-end sliding fractures, segmented placement is utilized to fully fill the fractures for short-term conductivity, whereas mixed placement is employed for long-term conductivity to achieve a balance in particle gaps and hinder the infiltration of coal fines. The findings of this study contribute to the understanding of proppant selection and placement strategies for efficient hydraulic fracturing in coalbed methane reservoirs.

Experimental investigation on coal fines migration through proppant packs: Assessing variation of formation damage and filtration coefficients

Coalbed methane reservoirs generate coal fines during production that cause irreversible damage to cleat conductivity. In severe scenarios, this can result in temporary closure of recovery operations from the gas well(s). In this work, we simulate the impact of coal fines on proppant conductivity. Four sets of experiments were conducted: effect of salinity – 0 to 3.5 NaCl wt.%, pH – 2 to 11, coal rank - anthracite, high volatile bituminous, and sub-bituminous; and 0.01 wt% additives – Sodium Dodecyl Benzene Sulfonate (SDBS) and Cetrimonium bromide (CTAB) and validated with established analytical models. Moreover, medical computed tomography of three extreme cases was conducted. Results showed that coal fines uniform distribution within a proppant pack does not cause greater conductivity decline than non-uniform distribution owing to clogging and straining. Additionally, results showed that anionic surfactants successfully dispersed coal fines. These research results can be applied to coalbed methane reservoirs, especially during the early water drainage phase, to optimise the impact of coal fines on proppant conductivity.

Study on Salt Dissolution Law of High Salinity Reservoir and Its Influence on Fracturing

For the high-salt reservoir of the Fengcheng Formation in the Mahu area, the production decreases rapidly due to the conductivity decrease after fracturing. The analysis shows that this has a great relationship with the special salt dissolution characteristics of the High salinity reservoir. In order to study the problem of salt dissolution pattern, the effect of different temperatures, the salt concentration of fracturing fluid, the viscosity of fracturing fluid, and injection rate on the rate of salt dissolution was evaluated by using the dynamic experimental evaluation method of salt dissolution. Through the grey correlation analysis of salt rock dissolution rate, it can be found that the degree of influence is from large to small which the influence of temperature is greater than fracturing fluid velocity, followed by fracturing fluid viscosity and, finally, fracturing fluid salt concentration. The results of compressive strength tests on salt-bearing rocks after dissolution show that the compressive strength is greatly reduced after salt dissolution by more than 60%. At the same time, the test results of proppant-free conductivity showed that the conductivity increased first and then decreased sharply after salt dissolution. This shows that in the early stage of salt dissolution, the flow channel will increase through dissolution. The rock strength decreases greatly with the increase of salt dissolution. As a result, collapse leads to a sharp reduction in the facture conductivity. Therefore, it is necessary to choose saturated brine fracturing fluid. In the proppant conductivity experiments, by optimizing the use of saturated brine fracturing fluid with 30/50 mesh or 20/40 mesh ceramic proppant with a sand concentration of 5 Kg/m2, a high facture conductivity can be achieved under high closure pressure conditions. Based on the above study, directions and countermeasures for improving high saline reservoirs are proposed, which point the way to improve the fracturing conductivity.

Optimization of long-term fracture conductivity with quartz: An experimental investigation

For the purpose of cost management, many companies and research institutions have carried out technical research on the replacement of ceramic with quartz sand as proppant. However, few studies have systematically carried out short-term and long-term conductivity evaluation experiments for quartz sand proppants with different particle sizes. It is urgent to conduct experiments on the conductivity of quartz sand, and optimize the fracturing design based on the experimental results. The conductivity is the key indicator of the fracturing effect. The greater the conductivity, the better the hydraulic fracturing effect, and the longer the effective period, the higher the fracturing benefit. In this study, by evaluating the long-term conductivity of proppant, the influence of the type of quartz sand proppant, proppant particle size and sand paving concentration on the fracture conductivity are studied. Main results show that 1) the proppant performance of quartz sand produced in Chifeng is better than that of produced in Tongliao; 2) The long-term conductivity experiment results show that the conductivity of quartz sand proppant produced in Chifeng is better than that of TL, and under the same sanding concentration and closing pressure, the larger the particle size of the quartz sand, the higher the conductivity, and the greater the decrease in conductivity with the increase of the closing pressure; 3) In the influence of sand paving concentration, when the sand paving concentration is 5 and 7.5 kg/m2, the conductivity increase with the increase of the sand paving concentration.

Using Laboratory Results from New Methods of Measuring Proppant Conductivity to Model Hydraulic Fractures in Reservoir Simulation

Purpose: Hydraulic fracturing processes are conducted to create new fractures in a rock to increase the size, extent, and connectivity of existing fractures. The American Petroleum Institute (API) developed two testing procedures for measuring conductivity of proppants in a laboratory setting, namely; the Short-Term Proppant Conductivity Testing Procedure and Long-Term Proppant Conductivity Testing Method. However, these laboratory testing methods have produced inconsistent results, with a significant coefficient of variance of ±80% from one test to the other even with the use of the same proppants and procedures. Thus, this work seeks to use an improved laboratory variance from Montana Tech conductivity measurements to model hydraulic fractures in reservoir simulation to evaluate how it performs or compares with field performance.
 Methodology: Montana Tech researchers have developed new proppant conductivity testing methods to lower this variance. These testing procedures showed more consistent results with an average variance of ±7.6% and ±14.3% in ceramic and sand proppants respectively. These tests were all done at laboratory conditions and therefore this work used field production data obtained from the Willison Bakken Formation and an arbitrary high permeability value as a benchmark against the fracture models built using laboratory results from the new methods of measuring proppant conductivity testing by Montana Technological University.
 Findings: The conductivity values corresponding with 6,500 psi closure stress obtained for sand and ceramic were 2,133.5 md-ft and 4,870.3 md-ft respectively. The high permeability model recorded an incremental recovery increase of 42% over the unfractured model. Similarly, the laboratory sand and ceramic models had an incremental recovery increase of 12.9% and 33% respectively over the unfractured model. The dimensionless fracture conductivity for the laboratory sand, laboratory ceramic and high permeability models were 1,246, 2,844 and 233,577 respectively. Generally, laboratory conductivity overestimates field performance, however, this work did not show an improvement in modeling fractures using laboratory data as a result of the extremely low porosity and permeability values of the Bakken wells used for the study and the limitedness of the software package used. Simulation of low permeability reservoirs is still an area in development as traditional models often fail to produce results that match the physics. It is possible that as simulation methods for these types of reservoirs improve, the new laboratory data for fracture conductivity will prove beneficial in modeling.
 Unique contribution to theory, practice and policy (recommendation): A sensitivity analysis should be performed in Petrel that starts with the laboratory fracture conductivity and ends with infinite fracture conductivity. This would help determine the effect of correctly measuring fracture conductivity. Again, a better technique in Petrel such as using a tartan grid is encouraged to better assess the performance of each of the fractures and lastly, more well data with associated measured porosity and permeability data is suggested for future works.

Research on Proppant Optimization and Field Test of Ultra-Deep Tight Conglomerate Sandstone Reservoir

Efficient development of deep tight reservoirs in the southern margin of the Junggar Basin requires stimulation technology, and effective propped hydraulic fractures are the key to successful stimulation. To optimize the proppant selected for reservoir stimulation, the important parameters of proppant selection were determined through the proppant conductivity evaluation experimental study and field test, considering the influences of high temperature and high closure pressure. The results show that closure pressure, temperature, and sand concentration have a great influence on the conductivity of the proppant pack. The conductivity of the proppant pack decreases by about 10% at high temperatures, which is because the high temperature will rupture more proppant and thus reduce proppant pack permeability. In the long term, the Scenario B placement pattern can maintain high conductivity, and the long-term conductivity is increased by 6–26% compared with the Scenario C placement pattern. Furthermore, increasing the proppant placement concentration is conducive to the long-term conductivity of the fracture. During the operation of the test well, the treatment pressure was stable, and the fractures were effectively propped. No proppant flowing back occurred in the test production after the fracturing treatment, which achieved the purpose of the evaluation well, provided support for the large-scale development of subsequent development wells, and ensured orderly development.

Research on Conductivity Damage Based on Response Surface Analysis

Hydraulic fracturing is an important means of developing unconventional oil and gas layers. The fracture conductivity of tight sandstone reservoirs after fracture is affected by many factors, such as the interaction between the fracturing fluid, water, and rocks; the fracturing materials; and the construction parameters. This paper improves the experimental process of the long-term conductivity test and provides insight into conductivity prediction and optimization based on the response surface test method. The test process is conducted in the following manner: (1) inject nitrogen to evaluate the fracture conductivity before fracturing fluid damage; (2) inject fracturing fluid to simulate shut-in; and (3) inject nitrogen again to evaluate fracture conductivity after the damage ability of the fracturing fluid. The single factor test results show that the lower the sand concentration is, the higher the fracturing fluid viscosity will be, and the longer the fracturing fluid retention time is, the greater the damage to the conductivity of the fracturing fluid will be. The response surface test results show that the order of factors affecting the retention of conductivity is fracturing fluid viscosity > sand concentration > fracturing fluid retention time. There is a certain interaction between sand concentration and fluid viscosity, and there is also a certain interaction between fluid viscosity and fluid retention time, but these interactions are not significant; when the fracturing fluid retention time is longer, there will be an interaction between the sand concentration and the fracturing fluid retention time. In addition, based on the model used to optimize the fracturing construction parameters from the perspective of proppant conductivity damage, the optimal solution is when the viscosity of the fracturing fluid is 1 mPa.s, the paved-sand content is 8.49 kg/m2, and the retention time of the fracturing fluid is 10 h. The maximum retention rate of the flow conductivity is 63.19%.

Experimental characterization of time-dependent mechanical behaviours of frac sand at high compressive stresses and implication on long-term proppant conductivity

Experimental characterization of time-dependent mechanical behaviours of frac sand at high compressive stresses and implication on long-term proppant conductivity

Experimental Investigation on the Fracture Conductivity Behavior of Quartz Sand and Ceramic Mixed Proppants.

In this paper, a series of fracture conductivity experiments were designed and conducted by an American Petroleum Institute (API) standard fracture conductivity evaluation system. The mixing proportion of quartz sand and ceramic was optimized. By the evaluation of the proppant breakage rate and sphericity analysis of mixed proppant with different sand volume proportions (PS), the proppant mixture conductivity evolution behavior was analyzed. Results of this study showed that the conductivity of mixed proppant was between that of pure ceramic proppant and pure quartz sand proppant under the same conditions. For 20/40 mesh mixed proppant, a small amount of ceramic (25%) in mixed proppant could obtain 1.27–3 times higher conductivity than pure sand, while 40/70 mesh mixed proppant required the addition of 50% or more ceramic. The crushing resistance of mixed proppant determined the decrease of conductivity with the increase of effective closure stresses. A logarithmic empirical model was further derived from the results, which could be used to forecast the performance of fracture conductivity at different effective closure stresses and sand volume proportions.

Assessment of Long-Term Proppant Conductivity

Long-term conductivity data is essential to predict the production performance of the fractured well. It is necessary to know its long-term conductivity when choosing Tianxiang ceramic to prop hydraulic fractures in Northwest China. Its long-term conductivity was evaluated using DL-2000 equipment. Testing time at each closure stress point is more than 7 h, though the procedure used is similar to the recommended practice for short-term proppant conductivity. This test also investigates how factors such as proppant concentration and proppant size affected long-term conductivity. The results show these factors have a significant effect on long-term conductivity. Conductivity increases as proppant concentration rises, contributing to the increase of proppant volume and fracture height. Large proppants provide higher conductivity because large proppants have higher pore space and higher proppant pack height. High experimental temperature increases proppant conductivity due to dissolution and migration of minor fines and impurities. Besides, due to compaction, conductivity declines with the increase of testing time. Therefore, short-term conductivity is higher than long-term conductivity, while conductivity drops as testing time lasts. The results imply that Tianxiang ceramic performs as well as other ceramic proppants. It can offer proppant conductivity required by stimulation and qualifies to stimulate oil and gas wells in China. The achievements of this experiment will benefit hydraulic fracturing stimulation.

Effective Stress Factor Analysis of Proppant for Multi-stage Fracturing in Horizontal Wells

In order to determine the effective stress factor of proppants during the multi-stage hydraulic fracturing operation in horizontal wells and select the appropriate proppant type, the analysis of the effective stress characteristics of proppants is carried out. This analysis considers the geomechanics and long-term production characteristics of multi-stage fractured horizontal wells in reservoirs like Xinjiang Mahu shale oil and Southwest China shale gas. The analysis of influencing factors is also carried out. The results show that, during the multi-stage hydraulic fracturing operation in horizontal wells, the stress on proppants is not only related to geological factors such as reservoir closure stress, but also closely related to total injection volume, cluster spacing, liquid type, injection displacement and post fracture management. First, increasing injection intensity, reducing fracture spacing, using low viscosity fracturing fluid, adopting high injection displacement and utilizing reasonable flowback system can effectively supplement reservoir energy, postpone the effective stress peak of proppants, and increase the effective conductivity of proppants. Second, the production performance analysis results of nearly 300 horizontal wells (from Xinjiang oil field, Erdos tight oil reservoir, Sichuan shale gas reservoir, etc.) shows that: the effective stress of proppants in horizontal wells is only 50–60% of that in vertical wells, which results in a different proppant selection criterion in the volume stimulation of horizontal wells and provides the geomechanics basis of replacing ceramsite proppant with quartz sand to reduce cost and increase efficiency. Based on the above conclusions, the field test of replacing ceramsite proppant with quartz sand was carried out. The proportion of quartz sand increased from less than 30% in 2014 to 69% in 2019. Without any impact on production, the annual investment cost was decreased by more than 1 billion yuan, which set a great example for the promoted low-cost development of unconventional oil and gas reservoirs under low oil price background.