Accurate Characterization of Porosity Heterogenity and Optimization of Testing Zone Selection in High-Heterogeneous Carbonate Reservoir: A Success-Story From East China

Abstract

Objectives: The study area is carbonate buried hill reservoir of Archaean group located at east of China. The paper introduced one workflow to characterize porosity heterogeneities distribution and calculated porosity value based on each porosity type by using a novel image-based plug-in application in a commercial E&P software platform. Methods: This workflow take advantage of a geostatistic method that generates a full-coverage image to accurately delineate heterogeneities. Conductive and resistive heterogeneities are automatically delineated on the image using thresholds on contrast and value. The porosity map is computed using an established method that computes the porosity distribution by applying Archie’s law to each value of the conductivity image and the map is also associated with the heterogeneities. Superimposing fracture traces and bed boundaries picked on the heterogeneity image allows an automatic classification of the heterogeneities: vuggy porosity along bed boundaries, vuggy porosity connected to fractures including fracture porosity, isolated vuggy porosity, connected (vug to vug) vuggy porosity and porosity within rock matrix. The contribution of these different pore types to the total porosity of the formation is calculated in addition to the geometric information of delineated pore space at each depth. In addition, the connectedness of the different types of porosity is quantified. Results: The porosity distribution spectrum shows very good match with fullimage character. Wide porosity spectrum is related to high heterogeneous zone and narrow porosity spectrum is related to homogeneous zone. Most of the connected vuggy porosity and vuggy porosity connected to fractures type has good permeability compared to matrix porosity and isolated vugs. The result of this analysis helps the client to have better understanding of their carbonate reservoir especially the reservoir quality and reduce the uncertainty during formation evaluation. At last, the zones selected for testing are proved to have very high oil production through acid fracturing. Novels: The quantitatively calculation of the porosity distribition provides very valuable information for proper evaluation of this complex reservoir and sweet spot identification. This method can be applied in the other part of the study area. Also, this work can be a very good example to follow in similar complex reservoir from any part of the world.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018