Method for judging fluid type of reservoir through acoustic porosity-neutron porosity differential

Abstract

The invention discloses a method for judging the fluid type of a reservoir through an acoustic porosity-neutron porosity differential, which relates to the technical field of oil and gas logging, geology and core test analysis. The method comprises the following steps: 1) accurately calculating shale content, rock compositions, acoustic porosity and neutron porosity of the reservoir through core data calibration logging and logging data environment correction; 2) excluding the influence of factors such as lithology, borehole diameter and mud invasion on an acoustic transit time and neutron data; and 3) establishing a standard for judging the fluid type of the reservoir by comparing the magnitude of the acoustic porosity and the neutron porosity and using the response difference of the acoustic transit time and the neutron data to the gas and formation water. In the method, non-fluid influence factors such as the lithology, borehole conditions, mud invasion and the like are excluded when the fluid type of the reservoir is judged, so the characteristics of the influence of different fluids on the acoustic transit time and the neutron data can be grasped truly, and the coincidence rate of judging the fluid type of the reservoir is improved from 70 percent currently to over 90 percent.

Description

technical field [0001] The invention relates to the technical fields of oil and gas well logging, geology and core test analysis, in particular to a method for judging reservoir fluid types by using the difference between acoustic porosity and neutron porosity. Background technique [0002] Reservoir fluid type discrimination is one of the key technologies in natural gas exploration and development. Utilizing the different responses of natural gas and formation water to acoustic transit time and neutron data is one of the common methods to identify reservoir fluid types [0003] The sonic porosity-neutron porosity difference fluid type discrimination method belongs to the innovation of scientific research methods in the field of natural gas exploration and development. Based on the different impact characteristics of sub-data, the relationship between the acoustic wave and neutron difference between natural gas and formation water is finally established, and this difference...

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Problems solved by technology

However, when the porosity is large, the neutron logging value is relatively large, and factors such as lithology, borehole conditions, and mud immersion have a great influence on the acoustic time difference and neutron data, especially the neutron data, directly using the curve Morphological discrimination The coincidence rate of reservoir fluid type discrimination is not high. According to statistics, the coincidence rate of reservoir fluid type discrimination usually only reaches about 70%, which brings great difficulties to the development and production of natural gas

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