松辽盆地乾安—长岭凹陷大中型岩性—构造复合型油气田形成特征

FORMATION CHARACTERISTICS OF LARGE-MIDDLE LITHOLOGIC-STRUCTURAL COMPOSITE OIL AND GAS FIELDS IN THE QIAN’AN-CHANGLING DEPRESSION OF THE SONGLIAO BASIN

周荔青 张淮

ZHOU Li-qing ZHANG Huai

西北大学, 地质系, 陕西, 西安, 710069 2. 中国石化, 华东分公司, 江苏, 南京, 210011

Department of Geology, Northwest University, Xi'an, Shaanxi 710069 China 2. East China Branch, SINOPEC, Nanjing, Jiangsu 210011 China

松辽盆地南部乾安 长岭凹陷下白垩统发育了多套优质烃源岩和三角洲前缘相砂岩储集层,形成了上、中、下3套成藏组合。在凹陷东部的华字井阶地,具备形成大中型构造—岩性复合型圈闭的各种有利条件:多期三角洲前缘相区纵横交错、相互叠加,经常出现岩性横向相变和上倾尖灭;以乾南潜伏古隆起带古地形为背景形成的继承性南北沉积微相分异;后期构造运动造成盆地东部抬升,使得东部砂体整体上倾尖灭;后期构造运动形成一系列小断裂,对砂体上倾方向产生遮挡;大型斜向水流与区域构造格局的有机配置;成岩作用造成储层致密化。岩性—构造复合圈闭形成于嫩江期及明水期,与大规模油气运移期配置良好,为形成华字井阶地一批大中型构造—岩性复合型油气田创造了条件。

Many sets of high-quality source rocks and delta-front-facies sandstone reservoirs were developed in the Lower Cretaceous of the Qian an-Changling Depression in the southern part of the Songliao Basin.And upper, middle and lower three sets of pool-forming assemblages were formed.The Huazijing Terrace in the eastern part of the Depression possessed various advantageous conditions to form large-middle struc-tural-lithologic composite traps: a) multiphase delta-front-facies areas were intersecting and superimposing each other, and the lateral facies changes and updip thinning-out of lithology often occurred; b) the differentiation of south and north inherited sedimentary microfacies generated on the background of paleotopog-raphy-the buried paleouplift zone in Qiannan area; c)paulopost tectonic movement resulted in the elevation of the East Songliao Basin, and made the eastern sandbodies mass updip thinning out; d)paulopost tectonic movement resulted in a series of minor faults, screening off the updip direction of sandbodies; e) large scale of oblique water current formed organic allocation with regional structural patterns; and f) diagenesis resulted in the compaction of reservoirs.Lithologic-structural composite traps formed in the Nen-jiang and Mingshui perieds, and matched well with large scale of hydrocarbon migration periods.This provided good conditions to form a group of large-middle structural-lithologic composite oil and gas fields in the Huazijing Terrace.

https://doi.org/10.11781/sysydz200305445