Application of Facies-Constrained Inversion Technology to Prediction of Lacustrine Carbonate Reservoir in Yingxi, Qaidam Basin (Northwest China)

Abstract

The upper member of Xiaganchaigou formation in the Yingxi area of Qaidam Basin is located in the source sag, which is rich in hydrocarbon resources. However, exploration in the past three decades has not resulted in significant oil and gas discoveries. One reason is that there is not a good understanding of reservoir rock types and distributions.This study, based on an integration of outcrops, cores and experimental data, proposes that Lacustrine carbonate reservoirs are widely distributed in the upper member of Xiaganchaigou formation, and have the characteristics of complex lithology, poor physical properties, strong heterogeneity and thin layer thickness. The result of the traditional reservoir prediction method cannot guide the oil-gas exploration and evaluation well because of the low precision and the unclear geological law. The formation, distribution and oil-gas accumulation of lacustrine carbonate reservoirs are controlled by the sag paleo-highs in the study area. Therefore, the authors propose a facies-constrained and frequency-divided inversion method based on sedimentary cycles, paleo-terrain and seismic logging facies constraints. The technical idea is to guide the facies-constrained modeling through the geological stratigraphy, palaeogeomorphology and lithofacies to construct the low frequency model, and then use the frequency-divided nonlinear inversion method to carry out the constrained inversion with the phasing model. The results show that the high quality reservoir area of the target layer in the Yingxi area is changing with the migration of the paleo-highs northward, and the favorable reservoir area is about 150km2. The prediction results are in good agreement with the actual drilling and geological rules, which provides an effective reference for the further exploration and evaluation of the area.

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