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Characteristics of Abnormal Pressure Systems and Their Responses of Fluid in Huatugou Oil Field, Qaidam Basin
Author(s) -
CHEN Xiaozhi,
XU Hao,
TANG Dazhen,
ZHANG Junfeng,
HU Xiaolan,
TAO Shu,
CAI Yidong
Publication year - 2009
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.2009.00111.x
Subject(s) - geology , pressure coefficient , geothermal gradient , salinity , pressure system , hydrocarbon , structural basin , petrology , oil field , permeability (electromagnetism) , pressure gradient , porosity , petroleum engineering , mineralogy , geotechnical engineering , geomorphology , chemistry , oceanography , biochemistry , physics , organic chemistry , membrane , geophysics , mechanics
Based on the comprehensive study of core samples, well testing data, and reservoir fluid properties, the construction and the distribution of the abnormal pressure systems of the Huatugou oil field in Qaidam Basin are discussed. The correlation between the pressure systems and hydrocarbon accumulation is addressed by analyzing the corresponding fluid characteristics. The results show that the Huatugou oil field as a whole has low formation pressure and low fluid energy; therefore, the hydrocarbons are hard to migrate, which facilitates the forming of primary reservoirs. The study reservoirs, located at the Xiayoushashan Formation (N 2 1 ) and the Shangganchaigou Formation (N 1 ) are relatively shallow and have medium porosity and low permeability. They are abnormal low‐pressure reservoirs with an average formation pressure coefficient of 0.61 and 0.72 respectively. According to the pressure coefficient and geothermal anomaly, the N 1 and N 2 1 Formations belong to two independent temperature‐pressure systems, and the former has slightly higher energy. The low‐pressure compartments consist of a distal bar as the main body, prodelta mud as the top boundary, and shore and shallow lake mud or algal mound as the bottom boundary. They are vertically overlapped and horizontally paralleled. The formation water is abundant in the Cl − ion and can be categorized as CaCl 2 type with high salinity, which indicates that the abnormal low‐pressure compartments are in good sealing condition and beneficial for oil and gas accumulation and preservation.