松南长岭断陷无机气成因类型及分布特征

Origin Types and Distribution Characteristics of Inorganic Natural Gas in Changling Fault Depression

摘要:

对长岭断陷CO2气地化分析表明，松南气田多数井的δ13Cco2值均大于8×103，均为无机成因，而东岭气田部分井的δ13Cco2值均小于10×103，属于有机成因。其中无机成因CO2气体中R/Ra值均大于1，表明其无机成因CO2都属于岩浆幔源成因。对长岭断陷地区钻井气测含量资料综合分析表明，无机成因CO2气的平面展布特征可划分为：高含CO2气区（>90%），位于中部及东北部，表现有NNE—NE向展布的趋势；中高含CO2气区（70%~90%），主要位于乾安次凹南部，总体表现为NNW—近SN向展布；中低含CO2气区（20%~50%），主要分布于2个地区。红岗地区，以NNE向为主。腰英台—达尔罕地区，以近SN向为主；南部的低含CO2气区。垂向上长岭断陷南北2个次凹中的CO2产出层位显著不同。北部次凹内的产出层位较高，主要以泉头组及其上的青山口组为主。南部的无机CO2气产出层位以断陷期营城组火山岩为主，少量为登娄库组。

Abstract:

Through analysis of geochemical analysis of CO2 gas in Changling fault depression, it is showed that the δ13Cco2 value of most wells in Songnan gas fields are more than 8×103 , so, the gas belongs to inorganic natural gas. While, others in parts of Dongling gas fields are less than 10×103. It indicates those belong to organic natural gas. The R/Ra value of inorganic natural gas is more than 1. It indicates those gas come from magmamantle. According to comprehensive analysis of the contents of measured drilling data, this area can be divided into four grades: ①areas of CO2 gas with high level (>90%). It locates in the central and northeastern part of Changling fault depression; ② areas of CO2 gas with mediumhigh level(70%~90%). It mainly locates in the southern of Qian'an subdepression; ③areas of CO2 gas with mediumlow level (20%~50%). It locates in Honggang and YingyaotaiDaerhan areas; ④low CO2 containing gas zone in southern of Changling fault depression. Producing layers are significantly different in vertically between north subdepression and south subdepression. Producing layers in north are much higher than south. It is mainly composed by Quantou and Qingshankou formation. In contrast, it mainly produced in volcanic rocks in Yingcheng formation and a little in Denglouku formation.