阅读说明：本技术 一种模拟气藏边底水侵入的模型以及求取水侵系数的方法 (Model for simulating gas reservoir edge and bottom water invasion and method for calculating water invasion coefficient ) 是由 张继成 包智魁 卢光夫 冯诗淼 李清清 范佳乐 于 2019-10-09 设计创作，主要内容包括：一种模拟气藏边底水侵入的模型以及求取水侵系数的方法。主要解决在实验室中模拟边底水气藏模型注入水的流动速度和分布会存在差异,且岩石尺寸固定、密封要求高的不完善的问题。该模型由平板岩心、上盖板、下凹槽及可伸缩式支点组成；平板岩心四周及底部采用高渗透岩心包围,模拟真实地层边底水侵入；上盖板布置有多组出气孔与岩心接触且利用橡胶作为密封；下凹槽四周及底部布置有可伸缩式支点,协助上盖板满足密封性的同时适用于模拟不同边缘形状的储层；可伸缩式支点侧面设有出水孔,通过管线连接高压泵组,利用高压泵组保持压力恒定模拟无限大地层水体或降低压力模拟有限地层水体。(A model for simulating the invasion of water at the bottom of gas reservoir and a method for calculating the water invasion coefficient are disclosed. The method mainly solves the problems that the flow speed and the distribution of injected water of a simulated edge-bottom water gas reservoir model in a laboratory can be different, and the rock size is fixed and the sealing requirement is high. The model consists of a flat rock core, an upper cover plate, a lower groove and a telescopic fulcrum; surrounding the periphery and the bottom of the flat rock core by adopting a high-permeability rock core, and simulating the invasion of water at the bottom of the edge of a real stratum; the upper cover plate is provided with a plurality of groups of air outlet holes which are contacted with the rock core and sealed by rubber; telescopic supporting points are arranged at the periphery and the bottom of the lower groove to assist the upper cover plate to meet the sealing property and simultaneously be suitable for simulating reservoir layers with different edge shapes; the side surface of the telescopic fulcrum is provided with a water outlet hole, the telescopic fulcrum is connected with a high-pressure pump set through a pipeline, and the high-pressure pump set is used for keeping the pressure constant to simulate infinite stratum water bodies or reducing the pressure to simulate limited stratum water bodies.)

1. A model for simulating the invasion of water at the bottom of a gas reservoir comprises a flat rock core (6), an upper cover plate (1), a lower groove (9) and a telescopic fulcrum (8);

the flat rock core (6) is 20cm long and wide and 15cm high, and the periphery and the bottom of the flat rock core are surrounded by high-permeability rock cores (5 and 7);

the flat rock core (6) is placed in 1 upper cover plate (1) and 1 lower groove (9), wherein the length and width of the upper cover plate (1) are 39cm, the height of the upper cover plate is 2cm, the length and width of the lower groove (9) are 39cm, the height of the lower groove is 27cm, and the wall thickness of the lower groove is 2 cm; the length and the width of 4 high-permeability cores (5) on the side surface are 25cm, 5cm and 15cm, and the length and the width of 1 high-permeability core (7) on the bottom are 30cm and 5 cm; the upper plate (1) is provided with 4 threaded connectors (3), the gas production connector (2) is connected to the threaded connectors (3), and the lower end of the gas production connector (2) is in contact with the upper end of the flat rock core (6), so that the gas production development process is realized; the front of the lower groove (9) is provided with 10 threaded connectors (3), the telescopic fulcrum is split into a main body and a water inlet connector (10), the main body is placed inside the lower groove (9), the water inlet connector (10) is placed outside the lower groove (10), and the main body and the water inlet connector are aligned with the threaded connectors (3) and then are connected in a rotating mode for fixing the rock core; the artificial rock core is sealed by the upper cover plate (1) and the lower groove (9), the screw (34) penetrates through the upper and lower plate threaded interfaces (36, 38) of the upper clamping plate (35) and the lower clamping plate (36), and the upper cover plate (1) and the lower groove (9) are fixed by matching with a nut to realize pressure sealing.

2. A method for determining water intrusion coefficients in a laboratory using the model of claim 1, the method comprising the steps of:

firstly, assembling the model as claimed in claim 1, wherein a gap of 5cm is reserved between the assembled core and the lower groove (9), and water in the gap is used for eliminating the difference of the flow speed and the distribution of water when a water injection well is arranged at the edge or holes are distributed on the side surface of the device for water injection;

secondly, sealing the rock core in the model of claim 1, and connecting pipelines according to a predetermined wiring diagram, wherein each group of pipelines is connected with a telescopic fulcrum on one side surface of the model; after connection, the shunting box is connected with a balance bottle (17) through a connecting pipeline (30), an injection gas tank (18) is connected with the balance bottle (17) through a connecting pipeline (31), a constant-current pump (16) is connected with the balance bottle (17) through a connecting pipeline (32), a connecting pipeline (29) is connected with the upper end and the lower end of the balance bottle (17), and a metering bottle (20) is connected with a gas production connector (2) through a connecting pipeline (33) to form a set of experimental system;

thirdly, opening a valve (21), connecting the model into a vacuum system, vacuumizing the core by using a vacuum pump, saturating water in the core after vacuumizing, and measuring the pore volume and the porosity of the core according to the saturated water amount of the core;

fourthly, using N for the water in the rock core treated in the third step ₂Purging and then measuring the original water saturation S _wiWater saturation S at the time of experiment stop _wCumulative water production W _pAnd the original volume coefficient B of the gas under the experimental conditions _giVolume coefficient of water B _wClosing the valve (21), discharging all gas which does not enter the rock core, injecting water into the gap through the water injection channel (14), and simulating the invasion of bottom water after the air inlet channel is converted into the water injection channel;

fifthly, recording accumulated water yield, pressure and time, and recording pressure difference delta p and time t until the experimental pressure is stable and unchanged; calculating geological reserve G by using the core porosity phi measured in the third step, and simultaneously using the original water saturation S measured in the fourth step _wiWater saturation S at the time of experiment stop _wCumulative water production W _pAnd the original volume coefficient B of the gas under the experimental conditions _giVolume coefficient of water B _wCalculating water invasion W _e；

Sixthly, calculating a water invasion coefficient B for simulating the invasion of water at the bottom of the gas reservoir by using the model according to a formula (1) and a formula (2) by combining the pressure difference delta p and the time t recorded in the fifth step;

W _e＝W _pB _w+GB _gi(S _w-S _wi) Formula (1)

B＝W _e/(. DELTA.p.t) formula (2).

The technical field is as follows:

the invention relates to a novel model for simulating gas reservoir edge bottom water invasion and a method for calculating a water invasion coefficient, which are applied to the field of petroleum engineering.

Background art:

in the development process of the gas reservoir with active edge bottom water, the production of the gas field is directly influenced by the edge bottom water invasion, so that the water content of a gas well rises quickly, the recovery ratio is reduced, and the efficient development of the gas reservoir is restricted, so that the edge bottom water invasion mechanism is deeply researched, a method for researching the edge bottom water invasion development process of the gas reservoir is found, the water invasion coefficient is obtained, and the method has important significance for guiding the production of the gas reservoir. At present, a water injection well is arranged at the edge of a rock core or holes are distributed on the side surface of the device to simulate edge water drive for simulating a gas reservoir edge-bottom water invasion model in a laboratory. The method is influenced by the heterogeneity of the rock core, the flow speed and the distribution of the injected water are different, the size of the rock is fixed, the sealing requirement is high, and the simulation is not real.

The invention content is as follows:

in order to solve the technical problems mentioned in the background technology, the invention provides a new model for simulating the invasion of bottom water of a gas reservoir and a method for calculating a water invasion coefficient.

The technical scheme of the invention is as follows: the core comprises a flat core, an upper cover plate, a lower groove and a telescopic fulcrum.

The length and the width of the flat rock core are 20cm, the height of the flat rock core is 15cm, and the periphery and the bottom of the flat rock core are surrounded by a high-permeability rock core; the flat rock core is placed in 1 upper cover plate and 1 lower groove, wherein the length and width of the upper cover plate are 39cm, the height of the upper cover plate is 2cm, the length and width of the lower groove are 39cm, the height of the lower groove is 27cm, and the wall thickness of the lower groove is 2 cm; 4 high-permeability cores on the side surfaces are 25cm long, 5cm wide and 15cm high, and 1 high-permeability core on the bottom is 30cm long, 5cm wide and 5cm high; 4 threaded connectors are formed in the upper plate, the gas production connector is connected to the threaded connectors, and the lower end of the gas production connector is in contact with the upper end of the flat rock core, so that the gas production development process is realized; the front of the lower groove is provided with 10 threaded connectors, the telescopic supporting point is split into a main body and a water inlet connector, the main body is placed inside the lower groove, and the water inlet connector is placed outside the lower groove and is in rotary connection after being aligned with the threaded connectors for fixing the core. The artificial rock core is sealed by the upper cover plate and the lower groove, the screw penetrates through the upper and lower plate threaded interfaces of the upper clamping plate and the lower clamping plate, and the upper cover plate and the lower groove are fixed by matching with the nut to realize pressurization sealing.

The method for solving the water invasion coefficient by using the model comprises the following steps:

firstly, assembling a model, wherein a gap of 5cm is reserved between the assembled core and a lower groove, and water in the gap is used for eliminating the difference of the flowing speed and the distribution of the water when a water injection well is arranged at the edge or holes are distributed on the side surface of the device for water injection;

secondly, sealing the rock core in the model, and connecting pipelines according to a predetermined wiring diagram, wherein each group of pipelines is connected with a telescopic fulcrum on one side surface of the model; after connection, the shunting box is connected with the balance bottle through a connecting pipeline, the injection gas tank is connected with the balance bottle through a connecting pipeline, the constant-flow pump is connected with the balance bottle through a connecting pipeline, the connecting pipeline is connected with the upper end and the lower end of the balance bottle, and the metering bottle is connected with the gas production joint through a connecting pipeline to form a set of experiment system;

thirdly, opening a valve, connecting the model into a vacuum system, vacuumizing the core by using a vacuum pump, saturating the core with water after vacuumizing, and measuring the pore volume and porosity of the core according to the saturated water of the core;

fourthly, using N for the water in the rock core treated in the third step ₂Purging and then measuring the original water saturation S _wiWater saturation S at the time of experiment stop _wCumulative water production W _pAnd the original volume coefficient B of the gas under the experimental conditions _giVolume coefficient of water B _wClosing the valve, discharging all gas which does not enter the rock core, injecting water into the gap through the water injection channel, and simulating the invasion of bottom water after the air inlet channel is converted into the water injection channel;

fifthly, recording accumulated water yield, pressure and time, and recording pressure difference delta p and time t until the experimental pressure is stable and unchanged; calculating geological reserve G by using the core porosity phi measured in the third step, and simultaneously using the original water saturation S measured in the fourth step _wiWater saturation S at the time of experiment stop _wCumulative water production W _pAnd the original volume coefficient B of the gas under the experimental conditions _giVolume coefficient of water B _wCalculating water invasion W _e；

Sixthly, calculating a water invasion coefficient B for simulating the invasion of water at the bottom of the gas reservoir by using the model according to a formula (1) and a formula (2) by combining the pressure difference delta p and the time t recorded in the fifth step;

W _e＝W _pB _w+GB _gi(S _w-S _wi) Formula (1)

B＝W _e/(. DELTA.p.t) formula (2)

The flat artificial rock core is manufactured into different types of rock cores according to the conditions of the aspects of the heterogeneity, permeability, porosity, sensitivity, interlayer and the like of an actual gas reservoir so as to meet the requirement of simulating the actual gas reservoir.

The invention has the following beneficial effects: the model provided by the invention has the advantages of simple structure and convenience in operation, solves the difference of flow speed and distribution of injected water, and solves the problem of high sealing requirement. In laboratory research, a simulation method for a gas reservoir edge bottom water invasion model is a method for arranging a water injection well at the edge of a rock core or arranging holes on the side surface of a device to simulate edge water drive. The method is influenced by the heterogeneity of the rock core, the flow speed and the distribution of the injected water are different, the size of the rock is fixed, the sealing requirement is high, and the simulation is not real.