Observation method for coal-bed gas well hydraulically created fracture

Abstract

The invention discloses an observation method for coal-bed gas well hydraulically created fracture. The method includes the steps that S1, tracer fracturing fluid is pumped into a coal reservoir, so that the pressure in the coal reservoir is increased to break the coal reservoir to form fracture, and the tracer fracturing fluid enters the fracture and supports the fracture; and S2, after a periodof time, the fracture condition in a section is visually observed by naked eyes and recorded along with the proceeding of underground coal mining work, and a sample of the coal reservoir is collectedso as to evaluate the condition of micro-fracture in the coal reservoir; then a fracturing fracture plane distribution diagram and a fracture 3D distribution diagram are drawn, and the fracturing effect is evaluated; and the tracer fracturing fluid comprises fluorescent tracing sand and a fluorescent tracing agent. According to the method, the fluorescent tracing sand and the fluorescent tracer agent are pumped into the fracture to generate a fluorescent effect, and the fracture can be observed through a direct observation method; the flow conductivity of the fracturing effect and the fractureforming effect in the micro-fracture can be analyzed and evaluated; and the fracturing effect can be evaluated more truly and accurately.

Description

technical field [0001] The invention relates to the technical field of coalbed gas exploration and development, in particular to a method for observing hydraulic fractures of coalbed gas wells. Background technique [0002] Coalbed methane well fracturing is the main technical means for coalbed methane exploration and development to increase production, and the effect of coalbed methane fracturing is one of the key factors determining the production capacity of coalbed methane. The shape, geometric size (length, width, height), orientation, conductivity, and communication with natural fractures of coal seam fracturing fractures are important indicators for evaluating fracturing effects. The monitoring of coal seam fracturing fractures has important guiding significance for optimizing fracturing design, formulating fracturing schemes, and deploying well pattern and spacing. [0003] At present, the monitoring methods for coalbed gas fracturing fractures mainly include micros...

AI Technical Summary

Problems solved by technology

Although microseismic and microfracture vector scanning monitoring are widely used in coalbed methane companies, these two methods also have limitations. For example, they are less reliable in monitoring fracture width and fracture conductivity; At the same time, they are all indirect monitoring, through data collection, data conversion and interpretation, the real reliability of cracks will be reduced

[0004] Tracer monitoring of fractures has been used in the field of oil development for a long time. Because most of the selected tracers are radioactive and polluting, their application in the field of coalbed methane is rare. In recent years, with the development of unconventional natural gas With the wide application of stage fracturing technology, the use of tracers to monitor the volume of fracturing fractures began to be applied; the tracer monitoring method is to inject tracers into coal reservoirs during the fracturing process, such as yttrium, lanthanum, cerium, and praseodymium , neodymium, holmium, samarium, europium, gadolinium, erbium, thulium and ytterbium and other trace elements, and then continuously take samples at the wellhead to test the concentration changes of each tracer marker in the sample to evaluate the fracturing effect and fracturing effect of each stage. However, the change of tracer concentration in the wellhead sampling test can only indirectly reflect the volume of fractured fractures, and there are also limitations that are not intuitive and accurate enough, and it is even helpless to monitor the fracture shape and distribution law.

[0005] The underground excavation observation method is a method of directly observing the shape and expansion law of coalbed methane well fracturing fractures in coal mine tunnels, excavation working faces, and mining working faces. It is an intuitive and accurate fracture monitoring method; but the underground excavation observation method is also There are some defects, such as a long period, when the mining conditions of underground coal mines are complex, quartz sand is mixed with coal powder, it is difficult to find proppant, so it is difficult to distinguish natural fractures from artificial fractures, and it is also difficult to evaluate the effect of fracturing on the transformation and connection of tiny fractures

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