Determination method of downhole formation porosity

Abstract

The invention provides a downhole formation porosity determination method. The method comprises the steps that the rock framework longitudinal wave slowness at the downhole set depth is determined according to the formation mineral volume content; the formation longitudinal wave slowness and formation transverse wave slowness at the downhole set depth are extracted according to array acoustic wave logging data; the formation porosity at the downhole set depth is determined according to the rock framework longitudinal wave slowness, the formation longitudinal wave slowness and the formation transverse wave slowness at the downhole set depth. According to the downhole formation porosity determination method, the formation porosity value is determined by adopting both the formation longitudinal slowness and the formation transverse wave slowness, the downhhole formation porosity can be precisely obtained, the obtained formation porosity value does not need to be corrected, the utilization rate of the array acoustic wave logging data is increased, and the accuracy of the formation porosity value is improved.

Description

technical field [0001] The invention relates to the technical field of oil and gas exploration, in particular to a method for determining the porosity of downhole formations. Background technique [0002] Porosity is the ratio of formation void volume to total rock volume. It is an important parameter to describe the physical properties of formation. Accurately obtaining formation porosity is a basic task for underground mineral exploration. The porosity of underground formations can be detected by using seismic and logging techniques. Logging technology mainly uses various instruments to detect physical signals in drilled wells, and then detects underground geological conditions and wellbore engineering conditions. [0003] In the prior art, a commonly used porosity determination method is: use indoor core compressional wave velocity-porosity, density-porosity experiments to establish empirical formulas, and then use logging instruments to measure physical signals such as ...

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Problems solved by technology

[0005] An embodiment of the present invention provides a method for determining the porosity of an underground formation, which is used to solve the problem that the porosity determination method in the prior art needs to perform lithology correction and compaction correction on the calculated porosity value, which increases the difficulty of field application

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