Characterization and prediction of shale oil sweet spot

Research tasks

Through the description and prediction of the characteristics of shale oil reservoirs in the target strata section of the district, the quality of the upper and lower "sweet spot" is comprehensively analyzed, and a set of characteristic prediction technology processes containing "geological sweet spot" (lithology, physical properties, source rock characteristics) and "engineering sweet spot" (clay content, rock brittleness) are formed, which provides technical support for the evaluation and deployment of shale oil and the design of horizontal wells.

Research ideas

First of all, the main characteristics of this project, porosity, rock brittleness evaluation is the core problem of "sweet spot" reservoir prediction. Shale oil pre-stack seismic "sweet spot" reservoir prediction technology starts from the study of logging data, based on seismic petrophysics theory. It first clarifies the "sweet spot" reservoir and its surrounding rock pre-stack elastic parameter characteristics and establishes a petrophysical interpretation template linked to the two through the orthographic tool. Through the optimization interpretation technology of multi-mineral, combined with the multi-pore media autocompatibility approximation petrophysics modeling technology, the sweet spot classification standard is established. Combined with the oil test data in the research area and the nuclear magnetic porosity logging, the characteristics of the sweet spot reservoir parameters of the destination layer section are established.                  

Logging evaluation model in sweet spot section

On this basis, the workflow of combining 2D poststack geostatistics inversion facies-controlled + 3D prestack geostatistical inversion are innovatively established, which gradually improves the identification accuracy of "sweet spot" reservoirs, solves the problem of thin reservoir space prediction, and generates a robust high-resolution acoustic impedance and Vp/Vs ratio parameter body, which provides input for subsequent petrophysical inversion. Based on the results of seismic petrophysics and high-resolution phased pre-stack geostatistical inversion, the petrophysical inversion obtains a high-precision porosity body, and the reservoir continuity and connectivity and the spatial distribution evaluation of the "sweet spot" reservoir are realized by setting the two-parameter constraint threshold values of porosity and rock brittleness. On this basis, Bayesian probability analysis based on PDF applies probability language to describe the credibility of "sweet spots". It allows each rock facies to be slightly overlapped in the probability space, so as to improve the interpretation accuracy of "sweet spots"

Research Results

This study uses relevant seismic data to carry out reservoir sweet spot characteristics and prediction through special processing methods such as pre-stack inversion, identify favorable areas, and lay a technical foundation for evaluating the deployment of wells in the area and improving the drilling rate of horizontal well "sweet spot" reservoirs. In the process of project implementation, the technical process of "sweet spot" reservoir prediction technology for shale oil petrophysics modeling. Prestack inversion was innovatively established to solve related geological problems. Finally the spatial distribution of "sweet spot" reservoir was carefully characterized.