阅读说明：本技术 一种复杂缝网条件下致密油精细物理模拟实验方法 (Fine physical simulation experiment method for compact oil under complex slotted screen condition ) 是由 梁彬 刘鹏 李闽 于家义 刘琦 于 2021-08-13 设计创作，主要内容包括：本发明公开一种复杂缝网条件下致密油精细物理模拟实验方法,包括：采用若干个方岩心组成整个岩心；在每个方岩心中部均切割出相应的岩心柱,对每个饱和油后的岩心柱进行核磁共振扫描；在进行每个吞吐轮次的致密油吞吐实验后分别对每个岩心柱进行核磁共振扫描；得到每个吞吐轮次的动用距离；根据吞吐轮次以及每个吞吐轮次的动用距离拟合得到吞吐轮次与动用距离的关系式；计算每个岩心柱的采收率；根据每个吞吐轮次每个岩心柱的采收率计算得到岩心总采收率；根据每个吞吐轮次的岩心总采收率拟合得到吞吐轮次与岩心总采收率的关系式。本发明获得的致密油动用规律实验结果准确,精细度高,能够准确认识并预测致密开发特征及极限采收率。(The invention discloses a compact oil fine physical simulation experiment method under the condition of a complex slotted net, which comprises the following steps: forming a whole core by adopting a plurality of square cores; cutting a corresponding core column in the middle of each square core, and performing nuclear magnetic resonance scanning on each core column after saturated oil; respectively carrying out nuclear magnetic resonance scanning on each core column after carrying out the compact oil huff-puff experiment of each huff-puff round; obtaining a movement distance of each handling round; fitting according to the handling rounds and the movement distance of each handling round to obtain a relational expression between the handling rounds and the movement distance; calculating the recovery ratio of each core column; calculating the total recovery rate of the rock core according to the recovery rate of each rock core column in each huff and puff turn; and fitting according to the total core recovery ratio of each handling round to obtain a relational expression between the handling round and the total core recovery ratio. The experimental result of the compact oil utilization rule obtained by the invention is accurate, the fineness is high, and the compact development characteristics and the ultimate recovery ratio can be accurately known and predicted.)

1. A compact oil fine physical simulation experiment method under the condition of a complex slotted net is characterized by comprising the following steps:

step S1, forming the whole core by adopting a plurality of square cores;

step S2, cutting a corresponding core column in the middle of each square core, and performing saturated oil on all the square cores and the core columns, so that the influence of the end face effect on the oil extraction process of the core columns can be effectively avoided;

step S3, performing nuclear magnetic resonance scanning on each core column after saturated oil to obtain initial T of each core column₂A spectrum;

step S4, installing the core column back into the square core, and then installing a plurality of same square cores into the core holder together for a tight oil huff and puff experiment;

step S5, after each huff and puff round of compact oil huff and puff experiment is carried out, nuclear magnetic resonance scanning is respectively carried out on each core column to obtain nuclear magnetic resonance T₂A spectrum;

step S6, and then obtaining the nuclear magnetic resonance T of each core column in each throughout round₂Initial T of spectrum and each core pillar₂Comparing the spectra, and comparing T₂Accumulating the widths of the core columns with substantial changes of the spectrums to obtain the used distance of each handling round;

step S7, obtaining a relational expression between the handling rounds and the handling distances according to the handling rounds and the handling distances of each handling round;

y₁＝a₁ln(t)+b₁

in the formula: y is₁Is a movement distance; t is the throughput round; a is₁、b₁Is a fitting coefficient;

step S8 Nuclear magnetic resonance T according to each throughput round₂Calculating the recovery ratio of each core pillar according to the porosity of the spectrum and the oil-water density difference;

s9, calculating the total recovery rate of the rock core of each huff and puff round according to the recovery rate of each rock core column of each huff and puff round;

in the formula: r_tThe total recovery rate of the rock core at the t-th moment; r_tjThe recovery factor of the jth core column at the time t; v_jVolume of jth core column; j is the number of the core pillars;

s10, fitting according to the total core recovery ratio of each handling round to obtain a relational expression between the handling round and the total core recovery ratio;

R＝a₂t²+b₂t+c₂

in the formula: r is total core recovery; t is the throughput round; a is₂、b₂、c₂Are fitting coefficients.

2. The method for the dense oil fine physical simulation experiment under the condition of the complex slotted-net according to claim 1, wherein the number of the square cores in the step S1 is 8.

3. The method for performing the dense oil fine physical simulation experiment under the condition of the complex slotted-net according to claim 2, wherein the size of the square core in the step S1 is 4.5cm x 4.5 cm.

4. The method for performing the dense oil fine physical simulation experiment under the complex slotted-net condition according to claim 3, wherein the size of the core column in the middle line of the step S2 is 2cm x 4.5 cm.

Technical Field

The invention relates to a compact oil fine physical simulation experiment method under the condition of a complex slotted net, and belongs to the technical field of oil and gas field development.

Background

The dense oil is a new hotspot for exploration and development of global unconventional oil and gas resources after shale gas, the dense oil in China is widely distributed and has huge reserves, the dense oil is a very realistic petroleum substitute resource, and the realization of large-scale economic development has important significance for the energy industry in China.

The compact oil refers to oil accumulation which has the overpressure matrix permeability of not more than 0.1mD (the air permeability is less than 1.0mD), has the porosity of less than 10 percent, is present in the crude oil rock in an adsorption or free state, or is not subjected to large-scale long-distance migration in reservoir rocks such as interbedded with the crude oil rock, adjacent compact sandstone, compact carbonate rock and the like. The compact oil reservoir has the characteristics of poor physical property of the reservoir, strong heterogeneity, micro-crack development and extremely low permeability. In view of the development characteristics of the existing compact oil, the conventional water flooding development mode is not applicable, oil extraction is generally carried out through development modes such as exhaustion, seepage, huff and puff, and the huff and puff is the most common compact development mode on site. For a specific tight reservoir rock sample, accurately revealing or characterizing the pore utilization condition of a tight oil reservoir at a specific position in a throughput mode is a precondition for accurately knowing a tight oil development mechanism.

Physical simulation is an important means for researching the development mechanism of the compact oil, and the development process and the extraction condition of the compact oil are simulated by a physical method through simulating specific oil reservoir conditions. However, the existing compact oil physical simulation experiment device mainly has the following problems:

1) the method for mining and metering the compact oil is single, and the error is large;

2) the compact oil throughput/diffusion distance measurement has high cost, great difficulty and low precision;

3) pore utilization conditions of dense oil at different swept positions cannot be represented finely;

4) the influence of complex seam net conditions on the mining effect of the compact oil reservoir cannot be researched.

Therefore, there is a need to develop a compact oil fine physical simulation experiment method under the complex slotted-net condition, which has the advantages of low cost, accurate measurement, simple operation, small experimental error and capability of accurately representing the leading edge propulsion condition and the pore exploitation degree of the experimental fluid in the rock sample.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention provides a compact oil fine physical simulation experiment method under the condition of a complex slotted net.

The technical scheme provided by the invention for solving the technical problems is as follows: a compact oil fine physical simulation experiment method under the condition of a complex slotted net comprises the following steps:

step S1, forming the whole core by adopting a plurality of square cores;

step S2, cutting a corresponding core column in the middle of each square core, and performing saturated oil on all the square cores and the core columns;

step S3, performing nuclear magnetic resonance scanning on each core column after saturated oil to obtain initial T of each core column₂A spectrum;

step S4, installing the core column back into the square core, and then installing a plurality of same square cores into the core holder together for a tight oil huff and puff experiment;

step S5, after each huff and puff round of compact oil huff and puff experiment is carried out, nuclear magnetic resonance scanning is respectively carried out on each core column to obtain nuclear magnetic resonance T₂A spectrum;

step S6, and then obtaining the nuclear magnetic resonance T of each core column in each throughout round₂Initial T of spectrum and each core pillar₂Comparing the spectra, and comparing T₂Accumulating the widths of the core columns with the changed spectrums to obtain the use distance of each handling round;

step S7, obtaining a relational expression between the handling rounds and the handling distances according to the handling rounds and the handling distances of each handling round;

y₁＝a₁ln(t)+b₁

in the formula: y is₁Is a movement distance; t is the throughput round; a is₁、b₁Is a fitting coefficient;

step S8 Nuclear magnetic resonance T according to each throughput round₂Calculating the recovery ratio of each core pillar according to the porosity of the spectrum and the oil-water density difference;

s9, finally, calculating the total recovery rate of the rock core of each huff and puff round according to the recovery rate of each rock core column of each huff and puff round;

in the formula: r_tThe total recovery rate of the rock core at the t-th moment; r_tjThe recovery factor of the jth core column at the time t; v_jVolume of jth core column; j is the number of the core pillars;

s10, fitting according to the total core recovery ratio of each handling round to obtain a relational expression between the handling round and the total core recovery ratio;

R＝a₂t²+b₂t+c₂

in the formula: r is total core recovery; t is the throughput round; a is₂、b₂、c₂Are fitting coefficients.

The further technical scheme is that the number of the square cores in the step S1 is 8.

The further technical scheme is that the size of the square core in the step S1 is 4.5cm multiplied by 4.5 cm.

The further technical scheme is that the size of the core column in the middle line of the step S2 is 2cm multiplied by 4.5 cm.

The invention has the following beneficial effects: the experimental result of the compact oil utilization rule obtained by the invention is accurate, the fineness is high, and the compact development characteristics and the ultimate recovery ratio can be accurately known and predicted.

Drawings

Fig. 1 is a schematic view of the entire core;

FIG. 2 is a schematic view of the oil-water front for a third throughput run;

FIG. 3 is a schematic representation of the oil-water front for a fifth throughput run;

FIG. 4 is T₂A map schematic;

FIG. 5 is a schematic representation of the mobility of a core string;

FIG. 6 is a diagram illustrating the relationship between throughput rounds and utilization distances;

FIG. 7 is a schematic representation of throughput runs versus total recovery;

FIG. 8 is a schematic diagram of an experimental system of throughput experiments in this embodiment;

FIG. 9 is a scatter plot of pressure at pressure points at different times.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the invention, the recovery ratio of the matrix block can be replaced by the recovery ratio of the core column, and the recovery ratio of the matrix block can also be linearly calculated based on the recovery ratio of the core column by adopting a linear dispersion method.

The invention relates to a compact oil fine physical simulation experiment method under the condition of a complex slotted net, which sequentially comprises the following steps:

step S1, forming a whole core by 8 square cores of 4.5cm multiplied by 4.5cm (shown in figure 1);

step S2, cutting a core column (shown in figure 1) of 2cm multiplied by 4.5cm in the vertical direction at the middle part of each square core, and performing saturated oil on all the square cores and the core columns;

step S3, performing nuclear magnetic resonance scanning on each core column after saturated oil to obtain initial T of each core column₂A spectrum;

step S4, installing the core column back into the square core, and then installing a plurality of same square cores into the core holder shown in the figure 8 together to perform a tight oil throughput experiment;

step S5, after each huff and puff round of compact oil huff and puff experiment is carried out, nuclear magnetic resonance scanning is respectively carried out on each core column to obtain nuclear magnetic resonance T₂A spectrum; in the present invention, 1 throughput round is 1 day;

step S6, and then obtaining the nuclear magnetic resonance T of each core column in each throughout round₂Of spectra with each core pillarInitial T₂Comparing the spectra, and comparing T₂The widths of the core columns with the changed spectrums are accumulated to obtain the handling distance of each handling round, and the result is shown in table 1;

TABLE 1

Number of rounds of taking and putting	Distance for movement, cm
		1	9
2	13.5
		3	18
4	22.5
		5	27
6	27
		7	31.5
8	31.5
		9	36
10	36
		11	36
12	36
		13	36
14	36
		15	36

Step S7, obtaining a relational expression between the handling rounds and the handling distances according to the handling rounds and the handling distances of each handling round;

y₁＝a₁ln(t)+b₁ (1)

in the formula: y is₁Is a movement distance; t is the throughput round; a is₁、b₁Is a fitting coefficient;

the specific relational expression is as follows:

y₁＝5.5261ln(t)+2.8437

the limit oil-exploiting distance of the oil reservoir under the current handling working system can be predicted by using the formula;

step S8 Nuclear magnetic resonance T according to each throughput round₂Calculating the recovery ratio of each core pillar according to the porosity of the spectrum and the oil-water density difference;

step S9, calculating and obtaining the total recovery ratio of the rock core of each handling round according to the recovery ratio of each rock core column of each handling round, wherein the result is shown in Table 2;

in the formula: r_tThe total recovery rate of the rock core at the t-th moment; r_tjThe recovery factor of the jth core column at the time t; v_jVolume of jth core column; j is the number of the core pillars;

TABLE 2

S10, fitting according to the total core recovery ratio of each handling round to obtain a relational expression between the handling round and the total core recovery ratio;

R＝a₂t²+b₂t+c₂ (2)

in the formula: r is total core recovery; t is the throughput round; a is₂、b₂、c₂The fitting coefficients are shown in FIG. 7.

Binding to nuclear magnetic resonance T₂The spectrum enables the study of the degree of repetitive power generation and the porosity power generation at the same position.

The pressure fluctuation condition can be researched, a pressure response curve can be obtained, and the propagation condition and the fluctuation time of the injection pressure among the core slices are determined.

According to the pressure of the pressure measuring points at different time, a scatter diagram is made, and a curve is fitted to obtain a function of

Inlet end:

middle section pressure measurement point: y is₄＝a₄t²+b₄t+c₄

End: y is₅＝a₅ln(t)+c₅

As can be seen from the pressure response curves: the pressure at the inlet end shows a remarkable attenuation trend, and the pressure at the middle pressure measuring point and the pressure at the tail end show an increasing trend; the subtraction of the corresponding functions also results in an on-the-way pressure drop at different times.

The multipoint pressure measurement method is beneficial to monitoring the pressure propagation condition in the process of developing the compact oil in real time, and the obtained pressure model can be expanded to the underground condition through similar transformation, so that guidance can be provided for field personnel to determine the throughput period and optimize the throughput system.

Although the present invention has been described with reference to the above embodiments, it should be understood that the present invention is not limited to the above embodiments, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention.