Geological Modeling for the Strong Heterogeneity Fluvial Reservoirs: A Case Study of the Upper Permian Formation in Su6 Experimental Area, Ordos Basin, Northern China

Abstract

Although extensive researches have been conducted on the geological modeling of fluvial facies, some problems still need to be solved on how to characterize the strong heterogeneity of both fluvial facies architecture and reservoir quality. This paper, taking one low permeable fluvial gas field in Ordos Basin as an example, carries out studies on a new geological modeling method to characterize the strong heterogeneity of fluvial reservoirs, which has significant meaning for achieving the goal of optimizing and adjusting development plan and providing guidelines for similar reservoirs. The study area, Su6 Experimental Area, Ordos Basin, has about 270 wells, with minimum well space of 204m and a systematic coring of 87m approximately. The main frequency of 3D seismic data is 28Hz, covering an area of roughly 256km². The Datong fluvial outcrops in east of Ordos Basin, which is comparable to the study area, is selected to study the quantitative architectural features of fluvial reservoirs to guide the subsurface architecture modeling. A set of new geological modeling methods integrating subsurface and surface data is proposed as follows: (1) The object-based modeling algorithm is applied to build the reservoir architecture model. The key to the object-based modeling algorithm is the quantitative architecture information including the superimposition styles and scale of sand bodies, which can be based on the researches of Datong outcrop analogues. New algorithms are programed to characterize the various superimposition styles quantitatively. And quantitative scale of fluvial sand bodies is considered to control the spatial distribution of fluvial sand bodies more rationally. (2) On the basis of architecture model, the porosity model is established applying sequential Gaussian simulation method controlled with reservoir architecture model and trended with the impedance data derived from logging constrained inversion as the second variable. Permeability model then is obtained based on the same idea. The architecture and property model can be used to evaluate the compartmentalization and heterogeneity of the fluvial reservoir which is crucial to the preparation of development plan.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015