Performance Of Horizontal Wells Research Articles

Performance of a horizontal well in a bounded anisotropic reservoir: Part II: Performance analysis of well length and reservoir geometry

Abstract Evaluation of the performance of horizontal wells is an important aspect in the enhancement of their productivity. This study provides mathematical computations, and analysis for theoretical well and reservoir considerations. The study investigates how well design and reservoirs geometry affect the overall performance of a horizontal well in a completely bounded reservoir throughout its productive life. A horizontal well in a rectangular reservoir with completely sealed boundaries is considered and the effect of dimensionless well length L D \hspace{.25em}{L}_{\text{D}} , dimensionless reservoir length x eD \hspace{.25em}{x}_{\text{eD}} , and dimensionless reservoir width y eD {y}_{\text{eD}} on the pressure response over a given period of production using dimensionless time t D {t}_{\text{D}} is studied. The mathematical model used was derived using source and Green’s functions presented in part I of this study. Appropriate well and reservoir parameters are considered and the respective dimensionless parameters are computed which are then used in computing dimensionless pressure P D {P}_{\text{D}} and its dimensionless pressure derivative P D ′ \hspace{.25em}{P}_{\text{D}}^{^{\prime} } . From the computations, the results obtained are analysed in diagnostic log–log plots with a discussion of the flow periods. The results obtained indicate that an increase in dimensionless well length decreases pressure response during the infinite-acting flow at early times and during transition flows at middle time but increases the pressure response during the pseudosteady state flow at late times. The dimensionless reservoir width and length are observed not to influence dimensionless pressure response during the infinite-acting flow at early times and during the transition flows at middle time, only affecting the prevalence time of the flow periods. However it is observed that during the pseudosteady state flow at late times, dimensionless pressure response reduces with increased dimensionless reservoir length and width.

Research on Production Performance Prediction Model of Horizontal Wells Completed with AICDs in Bottom Water Reservoirs

With the advancement of completion technology for horizontal wells in bottom water reservoirs, Autonomous Inflow Control Devices (AICDs), which have achieved good results in recent years, have been widely used in the oil fields of the eastern South China Sea. Although some mathematical methods can be used to predict the production performance of horizontal wells, there is no dynamic prediction method for the production performance of horizontal wells completed with AICDs. In this work, a mathematical model of porous flow in the reservoir, nozzle flow in the AICD, and pipe flow in the horizontal well is established, and then a new model is presented for predicting the dynamic performance of horizontal wells completed with AICDs in bottom water reservoirs. The new coupling model is compared with two horizontal wells completed with AICDs in the bottom water reservoirs of the eastern South China Sea, and the results indicate that the accuracy of the new model is sufficiently high to provide theoretical support for the further prediction of horizontal wells in the eastern South China Sea.

Simulation of the Production Performances of Horizontal Wells with a Fractured Shale Gas Reservoir

The production performances of a well with a shale gas reservoir displaying a complex fracture network are simulated. In particular, a micro-seismic cloud diagram is used to describe the fracture network, and accordingly, a production model is introduced based on a multi-scale flow mechanism. A finite volume method is then exploited for the integration of the model equations. The effects of apparent permeability, conductivity, Langmuir volume, and bottom hole pressure on gas well production are studied accordingly. The simulation results show that ignoring the micro-scale flow mechanism of the shale gas leads to underestimating the well gas production. It is shown that after ten years of production, the cumulative gas production difference between the two scenarios with and without considering the micro-scale flow mechanisms is 19.5%. The greater the fracture conductivity, the higher the initial gas production of the gas well and the cumulative gas production. The larger the Langmuir volume, the higher the gas production rate and the cumulative gas production. With the reduction of the bottom hole pressure, the cumulative gas production increases, but the growth rate gradually decreases.

Impact of Polymer Rheology on Gel Treatment Performance of Horizontal Wells with Severe Channeling

Summary Gel treatment has been a cost-effective method to control the conformance of a reservoir with severe heterogeneity problems. The water channels in such reservoirs can be classified as open fractures or high permeability porous media with pore-throat network. Many simulation studies have been conducted to discuss gel treatment performance for conformance control. However, nobody considered the polymer rheology difference in open fractures and porous media in simulation. Previous simulation studies also ignored the residual resistance factor as a function of rock permeability rather than a constant parameter. In this study, a conceptual simulation model was established to simulate the linear flow system for the reservoir with horizontal wells considering the two factors mentioned above. The results demonstrate that the gel treatment always provides the better placement results in the open fracture type channel than pore-throat network type channel. Moreover, it is very necessary to consider residual resistance factor as a function of permeability, which is based on the experimental results and can provide much greater plugging efficiency in the higher permeable channels than constant residual resistance factor. Sensitivity analysis studies and multifactor analysis indicate that increasing oil viscosity and permeability ratio has a strong positive influence on conformance control results, which indicate in-situ gel treatment can be better applied in heavy or viscous oil reservoirs with fracture-like channels. Besides, the results also indicate that in reservoirs with severe channeling problem where channel velocity was high, the differences of gelant placement and profile improvement in models with two different types of channels could be enlarged greatly.

Performance of Horizontal Wells Completed in Unconsolidated Sand: Case Study Niger-Delta

Drilling and completion of horizontal wells have been proven to be a productive and profitable project, in comparison with the performance of the conventional vertical wells. However, in Nigeria there are very few application of horizontal wells as open-hole, this is largely due to the unconsolidated nature of Niger-Delta sands. This study examined the completion of open-hole horizontal wells with a case study of a field which is located within the Niger-Delta region in Nigeria. Two (2) wells which have been successfully drilled and completed were sampled. To achieve this, the performance of the completion option was examined using an analytical approach. This implored the Joshi’s model and Vogel’s equation to construct the Inflow Performance Relationship (IPR) plot. The vertical lift performance (VLP) was considered by employing Gilbert’s method. From the combined plots, the optimum operating condition of the wells indicated that well A has a productivity index of 1.039 Stb/day/psi with a maximum flow rate of 3250 Stb/day, while well B has a productivity index of 1.156 Stb/day/psi and maximum rate of 3370 Stb/day. The results show that horizontal well projects executed in fields within the Niger-Delta region can be expected to produce at good rates as obtained in other regions of the world. With the production capacity shown by these wells, improved conventional ultimate recovery is assured. Keywords: Horizontal Well, Inflow Performance Relationship, Open-hole, Productivity index, and Vertical Lift Performance. DOI: 10.7176/JEES/11-10-07 Publication date: October 31 st 2021

Study on Deliverability Evaluation of Staged Fractured Horizontal Wells in Tight Oil Reservoirs

At present, the existing deliverability evaluation models mainly consider the impact of specific factors on production, and the description of the complex fracture network structure primarily remains at the stage of an ideal dual-pore medium with uniform distribution. However, this cannot reflect the actual fracture network structure and fluid flow law of fractured horizontal wells. Thus, in this paper, a non-uniform fracture network structure is proposed considering the influence of the threshold pressure gradient and stress sensitivity characteristics on the production performance of horizontal wells. The stress sensitivity and the fractal theory are combined to characterize the permeability of the complex fracture network, and a three-zone compound unsteady deliverability model for staged fractured horizontal wells in tight oil reservoirs is successfully developed. Laplace transformation, perturbation theory, and numerical inversion are applied to obtain the semi-analytical solution of the proposed deliverability model. The reliability and accuracy of the analytical solution are verified by the classical tri-linear flow model and an oil field example. The effects of related influential parameters on the production of horizontal wells are analyzed. The deliverability evaluation method proposed in this paper can provide a theoretical basis for formulating rational development technology policies for tight oil reservoirs.

Integrated Simulation for Hydraulic Fracturing, Productivity Prediction, and Optimization in Tight Conglomerate Reservoirs

With the development of advanced horizontal drilling and multistage hydraulic fracturing techniques, the productivity of unconventional tight oil such as that found in the Baikouquan Formation of the Mahu Sag in the Junger Basin has been increasing. The Mahu oilfield is the largest tight conglomerate reservoir in the world. However, predicting the productivity of fractured horizontal wells in tight oil remains a challenge due to the high heterogeneity of the reservoir and complexity of its hydraulic fractures. Therefore, this study proposes a workflow for coupled geological modeling, along with fracturing and reservoir simulations in tight conglomerate reservoirs. Taking well block Ma131 as an example, a three-dimensional geological model is first built according to the results of geophysical research. The unconventional fracture modeling is used next to establish a fracturing simulation. Given the lack of natural fractures and the high concentration of conglomerate in the study area, the method of the multiple groups of microscale natural fractures is used to simulate the impact of gravel on fracture propagation. The feasibility of the method is verified with microseismic monitoring data and treating curves. Thereafter, an unstructured grid and the INTERSECT reservoir simulator are used to simulate the production performance of horizontal wells. The stress sensitivity effect of the rock matrix and fractures and the changes in the formation flow field caused by fracturing are considered in the reservoir simulation. Hydraulic fractures are found to be unable to form complex fracture networks easily under the conditions of high stress difference, high gravel content, and undeveloped natural fractures. However, they show the characteristics of macroscopic simplicity and local branching. Reducing cluster spacing can increase the complexity of hydraulic fractures and the productivity of horizontal wells. Finally, the proposed integrated simulation process is used to optimize well spacing, fracturing stimulation parameters, and the production system. Overall, the study serves as a guide for maximizing the production and economic benefits of tight conglomerate reservoirs.

Inflow Performance Analysis of a Horizontal Well Coupling Stress Sensitivity and Reservoir Pressure Change in a Fractured-Porous Reservoir

Abstract Stress sensitivity has always been a research hotspot in fractured-porous reservoirs and shows huge impacts on well productivity during the depletion development. Due to the continuous reservoir pressure change, accurate evaluation of stress sensitivity and its influence on well productivity is of great significance to optimize well working system. Taking horizontal well trajectory as the research object, the principal focus of this work is on the analysis of inflow performance for a horizontal well coupling stress sensitivity and reservoir pressure change in a fractured-porous reservoir. Firstly, a relationship between permeability damage rate and stress sensitivity coefficient was established to quantitatively evaluate the influence of reservoir pressure and stress sensitivity on reservoir permeability. Secondly, considering stress sensitivity and reservoir pressure drop, a set of practical productivity equations were derived for a horizontal well in a fractured-porous reservoir by adopting the equivalent seepage resistance method. Finally, the influence of relevant important factors on the inflow performance of horizontal wells was discussed in depth. Results show that a positive correlation exists between stress sensitivity coefficient and maximum permeability damage rate. At the same maximum permeability damage rate, high initial reservoir pressure corresponds to low stress sensitivity coefficient. In general, stress sensitivity coefficient mainly ranges from 0 to 0.2. Reservoir pressure change drastically affects the production dynamic characteristics of horizontal wells, and both the inflow performance curve and the production index curve decline and shrink as reservoir pressure decreases. Stress sensitivity is negatively correlated with horizontal well productivity, and the inflow performance/production index curve bends closer to bottom-hole pressure axis, and an inflection point can be observed with the aggravation of stress sensitivity. In addition, horizontal wellbore length and initial reservoir permeability also show significant effects on the inflow performance and are positively correlated with well productivity. For water cut, it has little effect on the well production when bottom-hole pressure drawdown is low, but its effect gets stronger as the drawdown becomes higher. Meaningfully, depending on these newly established productivity equations, a reasonable production system can be quantitatively optimized and achieved for the horizontal wells in fractured-porous reservoirs.

GINI coefficient: An effective way to evaluate inflow profile equilibrium of horizontal wells in Shengli Oil Field

A new Inflow Gini Coefficient (GN) is introduced to directly and quantitatively to evaluate the equilibrium of horizontal well inflow profile. GN reflects to the difference of inflow profiles between actual well and ideal well simulated by a 3D oil-water black oil model. GN ranges from 0 to 1, and profile becomes more unbalanced with larger GN. 70 sample wells in Shengli Oilfield have been statistically studied to relate GN to production performance parameters, and then, 0 < GN < 0.1 is classified as balanced grade, 0.1 < GN < 0.3 as unbalanced grade, while GN > 0.3 as extremely unbalanced grade. GN selected the best schemes of profile control for 20 application wells, and averagely increased daily oil production from 13.9 m3/d to 20.2 m3/d, decreased water cut from 82.5% to 75.6% when GN dropped from 0.246 to 0.127. Further, the variation of daily oil production and water cut after profile control is found to increase exponentially with linear decrease of GN. It can be concluded that, GN provides effective guidance for inflow control of horizontal well to ensure successful results, the performance of horizontal well with more unbalanced inflow profile, especially GN > 0.3, always has great potential to be improved.

A study of the mechanism of nonuniform production rate in shale gas based on nonradioactive gas tracer technology

AbstractThe performance of horizontal wells in shale gas is controlled by multiple factors, and there is a difference in gas production rate between different fracturing stages. However, the mechanism of the nonuniform gas production rate is still not clear. In this paper, a typical shale gas well in the Longmaxi formation was selected to conduct the performance evaluation based on the nonradioactive gas tracer technology. The gas production profile was obtained, and the production feature of each stage was analyzed. On this basis, the production differences between fracturing stages were compared in four aspects: reservoir physical properties, distribution of natural fracture, parameters of fracturing operation, and technology of temporary plugging re‐orientation. The effect of various factors on the contribution of each stage was analyzed. And then, the mechanism of the nonuniform gas production rate was clarified. Finally, relevance analysis was performed to determine the main controlling factors, and a mathematical model for characterizing the nonuniform gas production rate feature was established by adopting the nonlinear regression method. This study provides a reliable basis for optimal fracturing designing and reasonable production planning.

Installation and performance of horizontal wells for dewatering at municipal solid waste landfills in China

Vertical wells are conventionally used to lower leachate levels or pressures in municipal solid waste (MSW) landfills. However, they are not always efficient or even effective, and in some circumstances retro-fitted horizontal wells represent a potential alternative. However, horizontal wells can be difficult to install and there is a lack of data on their performance. This paper describes the trial construction and operation of three horizontal wells in a landfill at Tianziling, China. The trial was used to develop an improved well installation technique, and to demonstrate the viability of the approach in a typical Chinese landfill. Three wells, between 50 m and 56 m in length, were successfully installed using an improved casing-protected directional drilling method. Average leachate flow rates of two wells were 10.66 m3/day and 3.93 m3/day, respectively. After 74 days of drainage, the maximum leachate level drawdown around the highest flow well was 2.7 m and its distance of influence was up to 50 m. Building on the experience gained at Tianziling, a wellfield comprising twelve horizontal wells having a total length of 1000 m was installed at Xingfeng landfill. After 157 days of drainage, a total volume of ~24,000 m3 leachate had been discharged and the leachate level had been lowered to near the elevation of the horizontal wells. This paper indicates the effectiveness of horizontal wells in reducing leachate level in landfills containing MSW typical of that generated in China, and gives data on installation and performance that may be useful for the design and operation of such an approach.

Prospects for the use of new technologies in assessing the impact of geological and technological risks

Nowadays, operator companies pay much attention to the introduction and development of technologies for development of oil fields using horizontal wells. This situation is due on the one hand to relatively greater efficiency of operation on horizontal wells, as compared with vertical, and problems typical for horizontal wells (low share of 10-30 % of the “working” part of the horizontal well, specificity of the influence of heterogeneity of the reservoir during stimulations, difficulty and water source control on the other hand. In addition, it is necessary to take into account a number of factors causing the exclusive use of horizontal wells: a restriction on the location of the wellhead relative to the target areas of the reservoir, a restriction on the number of wells, the development of fields with highly viscous and super-viscous oils, and the operation of unconventional (dense) reservoirs. The main objective of this work is to determine the prospects for the application of new technologies to increase the efficiency of operation of horizontal wells. It is impossible to describe the full picture without reflecting the results of the analysis of the performance of horizontal wells in field development, the problems of planning investments for drilling horizontal wells, as well as considering aspects of the economic evaluation of the use of technologies designed to improve the efficiency of horizontal wells. Much attention is paid to identifying the causes of declining oil production due to premature irrigation of horizontal wells. Various options for the occurrence of flow heterogeneity and their influence on the development of reservoirs using horizontal wells are considered.

An equivalent method to assess the production performance of horizontal wells with complicated hydraulic fracture network in shale oil reservoirs

The production performance of horizontal well with complex fracture networks remains a challenging issue. To more accurately evaluate the stimulation effect of fracture network on the reservoirs, an equivalent method is presented based on the extended finite element method (XFEM) and the Peaceman well model. We discretize the governing equations with finite volume method and solve the linearized equations with fully implicit scheme. The reliability of the equivalent method is validated against the available numerical method in the literature. After that, two cases of different fracture network structures are investigated. Results show that the equivalent method is feasible to assess the effect of fracture network on horizontal well production. And more broadly distributed fracture network has better enhancing effect. Meanwhile, fracture tips have little stimulation effect on the production. The findings are of benefit to provide us a simplified way to investigate the flow in reservoirs containing complex fracture network.

Performance of horizontal wells in composite tight gas reservoirs considering stress sensitivity

Tight gas reservoir (TGR) plays an important role in unconventional oil and gas resources. The existing seepage models for TGR rarely consider the effects of heterogeneity, stress-sensitivity, and the unsteady fluid exchange between matrix and fracture. Heterogeneity is common for tight gas reservoir which should be carefully considered in geological model. The stress-sensitivity effect of fracture is an important factor influencing the transient flow behavior of TGR. Ultra-low porosity and permeability cause the unsteady flow between matrix and fractures systems. So this paper introduced a mathematical model for the horizontal well in a dual-porosity composite tight gas reservoir with considering the stress-sensitivity effect and unsteady flow between matrix and fractures systems. Some mathematical methods including the finite Fourier cosine transform, perturbation technique, Laplace transform, superposition principle, Stehfest numerical inversion algorithm are used to solve the nonlinear partial differential equation. Different flow regimes are divided based on pressure transient analysis curves. The sensitivity analysis of related parameters is studied according to pressure transient analysis and rate transient analysis curves. The presented model and obtained results in this paper give better understanding on pressure and rate transient behaviors of composite TGR. Cited as : Zhao, K., Du, P. Performance of horizontal wells in composite tight gas reservoirs considering stress sensitivity. Advances in Geo-Energy Research, 2019, 3(3): 287-303, doi: 10.26804/ager.2019.03.07

Principles of rapid design of an inflow control device completion in homogeneous and heterogeneous reservoirs using type curves

This paper discusses the development and application of universal type-curves for the design of Advanced Well Completions (AWCs) equipped with passive (non-adjustable), flow control devices {a.k.a. Interval Control Devices (ICDs)}. This work provides an innovative, rapid approach to their design without the need for numerical simulators.AWCs equipped with ICDs aim to delay the early breakthrough of unwanted fluids in wells constructed close to a reservoir fluid contact. An uneven inflow profile due to reservoir permeability heterogeneity, multiple fluid contacts or an undulating well path needs to be managed. In addition, the Heel-to Toe effect (HTE) by frictional pressure loss due to fluid flow along the length of the completion interval also promotes a non-uniform inflow profile.The main AWC design challenge is to balance the trade-off between loss in well productivity from the added flow restrictions and the benefit of an improved inflow profile. This paper reviews the development of the analytical modelling of the inflow performance of horizontal wells with ICD completions, It presents new semi-analytical, mathematical models describing the ability of AWCs to mitigate production problems created by (reservoir) permeability heterogeneity and the (in-well) HTE. New dimensionless numbers allow the development of universal type-curves (TCs) for AWC design. The new workflow is illustrated for several case studies and the results validated by their good agreement with calculations made with the standard “well-reservoir” numerical simulator employed by engineers for this task.This novel approach for rapid analysis of the implications of well log data, such as that obtained shortly before the beginning the installation of the well completion, is the latest addition to the well completion engineering toolbox.

Analysis of transient production rate performance of horizontal well in fractured low permeability reservoirs based on finite element method

The proportion of oil produced from low permeability reservoir has increased in China in recent years and the nonlinear seepage exists in low permeability reservoirs widely according to laboratory tests and field experiences. Most previous scholars' research only focus on threshold pressure gradient, which cause result less accurate than the model considering nonlinear section of the seepage characteristic curve when interpreting transient production rate performance due to nonlinear seepage and stress sensitivity. A mathematical model of horizontal wells in fractured low permeability reservoirs considering nonlinear coefficient is established in this paper, which is solved by finite element method (FEM). Sensitive analysis is conducted on relevant parameters including permeability modulus, nonlinear coefficient and so on. With the effect of nonlinear cross flow, the concaves of derivative curves of pressure and production rate become shallower and move to the right. The paper significantly improves the reliability of interpretation results of fractured low permeability reservoir production rate data. [Received: March 8, 2018; Accepted: July 5, 2018]

Analysis of transient production rate performance of horizontal well in fractured low permeability reservoirs based on finite element method

The proportion of oil produced from low permeability reservoir has increased in China in recent years and the nonlinear seepage exists in low permeability reservoirs widely according to laboratory tests and field experiences. Most previous scholars' research only focus on threshold pressure gradient, which cause result less accurate than the model considering nonlinear section of the seepage characteristic curve when interpreting transient production rate performance due to nonlinear seepage and stress sensitivity. A mathematical model of horizontal wells in fractured low permeability reservoirs considering nonlinear coefficient is established in this paper, which is solved by finite element method (FEM). Sensitive analysis is conducted on relevant parameters including permeability modulus, nonlinear coefficient and so on. With the effect of nonlinear cross flow, the concaves of derivative curves of pressure and production rate become shallower and move to the right. The paper significantly improves the reliability of interpretation results of fractured low permeability reservoir production rate data. [Received: March 8, 2018; Accepted: July 5, 2018]

Characteristics of transient pressure performance of horizontal wells in fractured-vuggy tight fractal reservoirs considering nonlinear seepage

Since the classical seepage theory has limitations in characterizing the heterogeneity of fractured-vuggy tight reservoirs, well test interpretation results are not consistent with actual production by far. Based on the nonlinear percolation theory, a new nonlinear seepage equation considering the boundary layer and yield stress was derived to describe the seepage characteristics of dense matrix blocks and the stress sensitivity and fractal features of fracture systems were characterized by applying the fractal theory. Thus, the nonlinear model of a horizontal well in a fractured-vuggy tight fractal reservoir was established naturally. Then the finite element method was applied to solve the bottom hole pressure based on the processing of internal boundary conditions. After solving the model, the seepage characteristics of different models were summarized by analyzing the bottom hole pressure dynamic curves and the sensitivity analysis of multiple parameters such the nonlinear parameter and fractal index were conducted. Finally, the practicality of the model was proved through a field application. The results show that the pressure dynamic curves can be divided into nine flow stages and the increase of the nonlinear parameter will cause the intensity of the cross flow from matrix blocks to the fracture system to decrease. The fractal index is irrelevant to the intensity of the cross flow while it decides the upwarping degree of the curve at the middle and late flow stages. On the basis of the results of the field application, it can be concluded that the model fits well with actual production and the application of this model can improve the accuracy of well test interpretation.

Rate Decline Analysis for Horizontal Wells with Multiple Sections

The widely used application of horizontal well makes it significant to effectively evaluate rate performance of horizontal well in oil and gas reservoir. However, most models in previous work only focus on rate decline analysis (RDA) of horizontal well with single section (HWSS); they hardly address the problem that production rate distributes nonuniformly along horizontal wellbore in analyzing rate transient behaviors. However, only some horizontal segments contribute to the total production rates, and the production of each section along horizontal wellbore is not the same in fact, which may be caused by reservoir heterogeneity, selective completion, and nonuniform formation damage along horizontal wellbore. Therefore, the effect of these phenomena on rate decline characteristics cannot be ignored. The aim of this paper is to propose an analytical model to investigate transient rate response of a horizontal well with multiple sections (HWMS). The compound type curves, including the normalized production curve, the normalized production integral curve, and the production integral derivative curve, are developed to distinguish the different cases. The influences of some sensitive parameters on decline curves are further discussed. Results show obvious differences on the decline curves between the HWMS and HWSS. The parameters are sensitive on decline curves, which explore the feasible application on production performance evaluation and parameters interpretation through history matching the production data with the compound type curves in this paper.

Inflow characteristics of horizontal wells in sulfur gas reservoirs: A comprehensive experimental investigation

Due to geological and engineering factors, there exist difficulties with the performance of horizontal wells in sulfur gas reservoirs. In this study, an experiment is conducted on the performance of a horizontal well in a sulfur gas reservoir using a multifunction injection and production system for horizontal wells, with results verified by numerical simulation. Eight experiments are undertaken, including three for the influence of heterogeneity, three for the influence of drawdown pressure, and two for the influence of wellbore pressure drop. Results indicate that the inflow profile of the horizontal well in the experiment agrees well with the numerical simulation. Further experiments are conducted to investigate the effects of formation heterogeneity, drawdown pressure, and wellbore pressure drop on horizontal well performance. Results show that (1) greater heterogeneity means greater fluctuation in gas distribution along the horizontal well. The recovery factor become higher with the permeability differential decrease. (2) There is found a critical drawdown pressure at which a stable supply of gas can be achieved. Meanwhile, at the first stage, the main reservoir gas supply (B5) hold the largest permeability with a short duration; at the second stage, the other cores become the main source of gas supply. (3) Wellbore pressure drop makes gas distribution along the horizontal well gradually decrease from heel to toe. The results of this study can be used to guide completion optimization and production system adjustment.