东营凹陷牛庄—六户地区高压油气藏成因与分布

FORMATION AND DISTRIBUTION OF ABNORMALLY HIGH PRESSURE OIL-GAS POOLS IN NIUZHUANG-LIUHU AREA OF DONGYING DEPRESSION

中国东部断陷湖盆下第三系洼陷区,普遍存在异常高的地层压力。牛庄—六户地区即为异常高压岩性油气藏富集区。其沙河街组第三段中、下部的前三角洲和深—半深湖相的大套泥岩为地下流体提供了良好的封闭条件。烃类生成、压实作用,蒙脱石脱水,水热增压及地层的封闭性是产生高压油气藏的主要原因。地层压力发育情况,砂体的发育,储集体的物性及暗色泥岩的生油条件主要控制着近源斜坡浊积扇,湖底浊积扇,三角洲坡脚滑塌浊积扇及三角洲斜坡席状砂四类高压油气藏的分布。深—半深湖相的近物源斜坡区为最有利的高压油气藏富集区。高压油气藏具初产高、油质好、压力下降快、埋藏深和储量小但数量多的特点。在牛庄—六户地区具良好的勘探、开发远景。

Occurrence of abnormal formation pressure is common in Eocene faulted depression basin of east China. Niuzhuang-Liuhu sag is characterized as lithologic oil-gas accumulation ares. with abnormal high pressure. The thick shale of foredelta and deep and semi-deep lake faeies in middle and lower parts of Shahejie formation has provided good sealing condition for formation fluid. The major causes of abnormally high pressure oil-gas pools are hydrocarbon generation, under compaction, montmorillonite dehydration, hydrothermal-pressure increasing and sealing. The distribution of the four types of abnormally high pressure oil-gas pools. Near-source slope turbidite fan, turbidite fan in bottom of lake, slump turbidite fan on the slope of delta, and delta slope sheet sand oil-gas pool is controlled by formation pressure development, sandbody development, physical properties of the reservoir sandbodies and petroleum-generating condition. The near-source slop area of deep and semi-deep lake facies is the most favorable accumulation area of abnormally high pressure oil-gas pools. These pools are characterized by high initial oil production, good quality of oil, rapid decrease of pressure, great depth burial, less reserve and large in number. Good exploration and development prospect can be expected in Niuzhuang-Liuhu area.