CN113586007A

CN113586007A - Method for determining flow rate of washing pump injection liquid of coal-bed gas well on site

Info

Publication number: CN113586007A
Application number: CN202111040458.6A
Authority: CN
Inventors: 王军; 刘发文; 吴文飞; 邓宇
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2021-11-02
Anticipated expiration: 2041-09-06
Also published as: CN113586007B

Abstract

The invention discloses a method for determining the field of the flow of a pump washing injection liquid of a coal-bed gas well, belongs to the technical field of coal-bed gas drainage and extraction, and aims to overcome the defect that the gas production rate of the coal-bed gas well is reduced due to improper control of the pump washing injection flow on site in the existing pump washing technology. The key point and the main application of the technical scheme of the invention are to summarize and obtain a method for conveniently and quickly determining the injection flow rate on the pump washing site on the basis of fully researching the characteristics of the motion law of the fluid at the bottom of the well in the drainage and production process of the coal bed gas well, observing the influence of a large number of pump washing with various injection flow rates on various parameters of the coal bed gas well and fully testing the pump washing site, namely, the method for conveniently and quickly determining the injection flow rate on the site is provided through the form of a formula and the specific application and implementation method of the formula. The method is applied to the pump washing construction of the coal-bed gas well, and the influence of the reduction of the gas production rate of the coal-bed gas well caused by improper injection flow in the previous pump washing is well avoided.

Description

Method for determining flow rate of washing pump injection liquid of coal-bed gas well on site

Technical Field

The invention belongs to the field of coal bed gas exploration and development, and particularly relates to the technical field of coal bed gas drainage and extraction.

Background

In the drainage and production of the coal bed gas well, solid-phase impurities such as coal dust and the like inevitably produced enter the oil well pump and are blocked, the pump is generally checked after the pump is blocked, but the flow pressure of the coal bed gas well is greatly increased and the production is stopped for a long time, and the gas yield is generally reduced after the pump is checked. In order to avoid a series of bad influences caused by pump detection, the coal-bed gas well needs to be washed regularly to clean solid-phase impurities such as coal dust in a shaft and a production tubing string, so that the coal-bed gas well can be continuously produced for a longer time to avoid the reduction of gas production.

The current common pump washing method is to inject liquid with a certain flow rate at a certain pressure through a large four-way of a well mouth in the production of a coal-bed gas well, and simultaneously improve the discharge capacity of extraction equipment, so that solid-phase impurities such as coal dust and the like in a shaft and an oil-well pump of a production tubing string (including) are cleaned out of the well. However, no scientific and normative method is formed for the specific determination and control of the injection flow rate in the pump washing site. Therefore, the phenomenon that the gas production rate is reduced due to the fact that the bottom hole pressure is increased, external liquid invades a reservoir stratum and casing pressure is reduced due to overlarge injection flow is mostly generated in the pump washing; or because the injection flow is too small, the bottom hole pressure is greatly reduced, the reservoir flow pressure is excited, the casing pressure is greatly increased, and the gas production is greatly increased, so that the gas production of the coal-bed gas well suddenly rises after a period of time of washing the pump, the yield is unstable, and the final yield is reduced.

Disclosure of Invention

The invention aims to overcome the defects of gas production of the coal-bed gas well caused by improper control of field pump washing injection flow in the existing pump washing technology, and provides the pump washing device which can quickly determine injection displacement, is convenient to implement, can avoid abnormal and large fluctuation of bottom hole flowing pressure, and can prevent external fluid from invading a reservoir stratum, produce gas stably and realize casing pressure stability during pump washing, thereby avoiding the influence of gas production reduction of the coal-bed gas well caused by pump washing.

The technical scheme adopted by the invention for solving the technical problem is as follows:

1. determining reservoir produced water flow Q through average produced water flow of one week before near-washing pump of coal-bed gas well₂Determining the discharge flow rate Q of the well head through the maximum stroke frequency of the pumping unit₃The injection flow rate Q is determined by₁(the positions and the relations of the parameters are schematically shown in the figure 1 in the specification):

Q₁=n×（Q₃- Q₂) … … … … … … … … … … … … … … (formula 1)

In the formula: q₁Well head injection flow, m³/h；

Q₂Bottom hole reservoir water production flow, m³/h；

Q₃Discharge flow at well head, m³/h；

n-injection flow control coefficient.

n is within the range of 0.95-1.00, and the value of n is gradually increased by stages according to the pump washing.

The range of n is controlled to be between 0.95 and 1.00, and the numerical value of the n is gradually increased in stages according to the increase of the pump washing time, the method is summarized on the basis of fully researching the flowing rule of the drainage and production fluid and observing through a large number of pump washing phenomena, and the method is used for avoiding that the bottom hole pressure rises and external fluid invades and pollutes the reservoir stratum because the drainage flow is smaller than the sum of the injection flow and the reservoir stratum water production flow, so that the influence on the gas production of the coal bed gas well is caused. Therefore, n is controlled to be more than or equal to 0.95 and less than or equal to 1.00, the numerical value of the n is gradually increased in stages according to the increase of the pump washing time, so that the discharge flow is properly larger than the sum of the injection flow and the reservoir water production flow, and the injection flow is gradually increased along with the increase of the pump washing time, so that the bottom hole pressure is properly reduced in a small range and finally stabilized and is properly lower than the reservoir pressure around a shaft, therefore, firstly, the phenomenon that external fluid invades the reservoir to pollute the reservoir and influence the gas production after pump washing is avoided, and meanwhile, the gas production during pump washing is prevented from being reduced.

In one complete pump washing construction, the value of n is not completely fixed, the value of n gradually increases along with the increase of the pump washing time, and finally, the value of n is stabilized at 1.00. The specific adjustment time is properly adjusted according to casing pressure change (under the condition of not adjusting the flow rate of the produced gas at the wellhead), and specifically comprises the following steps:

1) controlling n =0.95 at the beginning of pump washing;

2) controlling n =0.96 when the wellhead casing pressure begins to rise;

3) controlling n =0.97 when wellhead casing pressure rises by 0.01;

4) controlling n =0.99 when the wellhead casing pressure rises by 0.02;

5) and controlling n =1.00 when the wellhead casing pressure rises by 0.03.

The invention mainly provides a calculation formula and a set of specific use and implementation method of the formula.

The method has the characteristics that the characteristics and the law of a reservoir at the bottom of the coal-bed gas well, a casing wall, a shaft and fluid flow are fully utilized, and the influence of the pump washing on the gas production rate of the coal-bed gas well is well achieved on the basis of finishing the purpose of pump washing, namely cleaning out solid-phase impurities in the shaft and a tubing string.

Compared with the prior art, the method has the advantages that firstly, the method well avoids the influence of gas production reduction of the coal-bed gas well caused by pump washing, avoids large loss of the coal-bed gas well, generates good economic benefit, and secondly, the method for mastering and using the coal-bed gas well pump washing liquid injection flow field calculation method is simple and rapid, and does not need to increase any cost.

Description of the drawings: FIG. 1 is a schematic view of the flow direction of the wash pump, which is a schematic view of three parameters in the formula of the present invention.

The present invention is further described in detail by the following embodiments:

1. after the specific pump-washing coal-bed gas well is determined, the average hour output water flow of the well in nearly one week is called, and the numerical value is the Q value of the formula (1)₁=n×（Q₃- Q₂) Q in (1)₂Thereby determining Q₂The size of (d);

2. calculating the well discharge water flow Q by the maximum stroke number value of the pumping unit₃；

3. General formula (1) Q₁=n×（Q₃- Q₂) Calculating to determine Q₁And the size of the coefficient n in the formula (1) is determined along with the progress of the pump washing according to the following method:

1) controlling n =0.95 at the beginning of pump washing;

2) controlling n =0.96 when the wellhead casing pressure begins to rise;

3) controlling n =0.97 when wellhead casing pressure rises by 0.01;

4) controlling n =0.99 when the wellhead casing pressure rises by 0.02;

5) when the wellhead casing pressure rises by 0.03, n =1.00 is controlled, and then the wellhead casing pressure is controlled to be 1.00.

Claims

1. Formula Q for calculating flow of washing pump injection liquid in coal bed gas well production₁=n×（Q₃- Q₂) In the formula Q₁-wellhead injection displacement; q₂-bottom reservoir water production; q₃-wellhead discharge flow rate; n-injection flow control coefficient.

2. The specific application method comprises the following formula and a flow control coefficient n:

the size of the coefficient n is determined along with the progress of the washing pump according to the following method:

1) controlling n =0.95 at the beginning of pump washing;

2) controlling n =0.96 when the wellhead casing pressure begins to rise;

3) controlling n =0.97 when wellhead casing pressure rises by 0.01;

4) controlling n =0.99 when the wellhead casing pressure rises by 0.02;