Method for determining content of natural gas in medium and low maturity fine-grained rock
A technology of maturity and gas volume, applied in analytical materials, instruments, etc., can solve problems such as relative solubility error, complex composition, and greater risk.
Active Publication Date: 2020-10-30
INST OF GEOLOGY & GEOPHYSICS CHINESE ACAD OF SCI
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Problems solved by technology
However, due to the existence of a large amount of liquid hydrocarbons that contain dissolved gas, only using methane isothermal adsorption experiments will bring large errors in the determination of the adsorbed gas content of medium-low maturity fine-grained rock samples, which will affect the calculation results of free gas.
In addition, the composition of liquid hydrocarbons in fine-grained rocks is relatively complex, and the solubility calculated only by the black oil model has a large relative error, which will also affect the calculation results of dissolved gas.
[0005] Therefore, there are large relative errors in the current conventional methods for obtaining gas volumes in different states of occurrence of fine-grained rocks with medium and low maturity, which leads to the inability to accurately predict the amount of underground reservoir resources. There are greater risks in the exploration and development of layered natural gas
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[0098] Three samples from the Yanchang Formation in the Ordos Basin were selected (Table 1). The data of S1 and chloroform bitumen 'A' show that all three samples have high liquid hydrocarbon content. The samples were pulverized to 25-30 meshes to obtain 200g each of the original particle samples. Take 100g each of the original particle samples 1#, 2# and 3#, and perform Soxhlet extraction with chloroform reagent for 72 hours to remove the liquid hydrocarbons in the original particle samples, and obtain the particle samples 1# and 2# from which the liquid hydrocarbons were removed. and 3#.
[0099] Table 1 Sample characteristics
[0100]
[0101] The pore size range of 0.38-10nm was selected for research. Within this pore size range, 0.4nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 1.2nm, 1.5nm, 1.7nm, 2nm, 3nm, 6nm and 9nm were selected as representative pore sizes. According to the above representative pore diameters, the pore diameter range of 0.38-10nm is divided into the fo...
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Abstract
The invention provides a method for determining the content of natural gas in medium and low maturity fine-grained rock. The method comprises the following steps: providing an original sample and an oil removal sample; dividing a specific pore size range of fine-grained rock; carrying out molecular simulation to obtain a unit pore volume excess isothermal adsorption gas volume curve; obtaining thecalculated isothermal adsorption gas volume curve of the oil removal sample; obtaining the actually measured isothermal gas volume curves of the original sample and the oil removal sample; performingapproximation comparison on the actually measured isothermal gas volume curve and the calculated isothermal adsorption gas volume curve of the oil removal sample; determining whether to re-divide a specific pore size range according to an approximation comparison result, and obtaining and comparing a unit pore volume excess isothermal adsorption gas volume curve; obtaining the calculated excess isothermal adsorption gas volume curve of the original sample; deducting and calculated excess isothermal adsorption gas volume curve from the actually measured isothermal gas volume curve of the original particle sample to obtain a dissolved gas volume curve; and obtaining the dissolved gas volume of the fine-grained rock under any pressure. The method can accurately determine the content of the natural gas in the fine-grained rock.
Description
technical field [0001] The invention relates to a method for determining the natural gas content in medium-low maturity fine-grained rocks. Background technique [0002] Sedimentary rocks composed of clay-grade or silt-grade sediments with a particle size of less than 62 μm are called fine-grained rocks, which are important reservoir rocks for unconventional oil and gas such as shale gas and tight sandstone gas. In fine-grained rock reservoirs such as shale, the natural gas is mainly methane gas, including three different occurrence states of free gas, adsorbed gas and dissolved gas. Accurately obtaining the natural gas content, relative proportion and total gas content of different occurrence states in fine-grained rocks is of great significance for evaluating fine-grained rock gas reservoir resources and selecting gas reservoir development methods. [0003] At present, in the high-maturity fine-grained rocks in North America and southern my country (that is, fine-grained ...
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IPC IPC(8): G01N7/04
CPCG01N7/04
Inventor程明罗晓容俞雨溪雷裕红张立宽
OwnerINST OF GEOLOGY & GEOPHYSICS CHINESE ACAD OF SCI