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Low Contrast Pay Identification in the Shahejie Formation, Bohai Bay Basin, East ChinaNormal access

Authors: Y. Cui, G. Wang, X. Fan and H. Zhao
Event name: 81st EAGE Conference and Exhibition 2019
Session: Poster: Interpretation Development & Case Studies
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201901076
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.66Mb )
Price: € 20

Low contrast pay, i.e. the resistivity of oil-bearing intervals differ little from adjacent water-bearing intervals, will result in missing hydrocarbon-bearing reservoirs. In this study, 12 wells in the Qibei slope field in the Bohai Bay Basin is taken as a pilot research since part reservoirs in this filed exhibit low contrast phenomena. The objectives of this study are: 1) to understand the causes of low contrast resistivity pay in the study reservoirs, and 2) to construct and validate a methodology for recognizing low contrast pay. To achieve these objectives, routine core analysis was done and thin sections were prepared for point counting. Moreover, formation water salinity were analyzed. Three factors, namely water salinity, grain size and porosity, are identified as major controls on low contrast pay. In order to compensate the effects of variations in water salinity, grain size and porosity on fluid identification, a parameter, apparent resistivity indicator (ARI), was constructed using porosity, resistivity, and gamma ray. Oil bearing zones show high ARI values, and wet zones have low ARI values, whereas the zones with medium ARI values often produce both oil and water, which indicates promising result for recognizing low contrast pay.

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