东濮凹陷天然气分布成因及富集因素

东濮凹陷天然气资源非常丰富,纵向上主要集中在盐下沙三~4、沙四及盐间沙二下、沙三~1、沙三~3段;平面上则主要分布在凹陷北部中央隆起带上。现已探明的天然气,从化学组成上看有干气、湿气、凝折气;从成因上分析有油型气、煤系气及两者相互掺合的混合气。下第三系和石炭二迭系是两套主要生气源岩。由于早第三纪凹陷快速沉降,使下伏石炭二迭纪煤系进入二次生气期,同时使下第三系生油气岩系相当一部分进入高成熟生气阶段,形成丰富的气源。其上又有分布广、厚度大的膏盐作为良好的盖层,天然气不易散失,故导致凹陷中天然气的富集。

STUDY ON THE GENERATION, DISTRIBUTION AND ACCUMULATION CAUSE OF NATURAL GAS IN DONGPU DEPRESSION

Dongpu Depression is rich in natural gas resources. Vertically, natural gas is accumulated in Saline Lower sha-34, sha-4 and Inter saline sha-2, sha-31 , sha-33 sections; and areally it is accumulated in the central rise of the northern part. There are dry gas, wet gas and condensale gas regarding its composition. Accordong to its origin, there are coal gas, oil associated gas and mixture of the both. There appeared to be mixture ga's of biogenic and oil associated origin gas. Lower Tertiary and Carboniferous-Permian Sequences are the two chief source bed. Rapid subsidence of lower Tertiary caused the secondary gas generation of the underying coal bed systems within the Carboniferous-Permian sequences, and als6 caused over-maturation of many oil source beds in lower Tertiary. The overlying thick evapofites series (salt arid gypsum predominantly) was a perfect cap rock.