Accumulation characteristics of shallow natural gas in Daqing placanticline in the northern Songliao Basin

In recent year, shallow natural gas is making a breakthrough in Heidimiao oil layer in Daqing placanticline in the northern Songliao Basin, and a serious of new natural gas reservoirs were found. In order to obtain the accumulation characteristics of shallow gas, through the study of fine geology, isotopic analysis, genetic types of chart, the formation condition of shallow gas was analyzed and its accumulation combination was determined. In addition, the genetic type and gas reservoir types were analyzed and the main controlling factors of gas reservoir were summarized. Results indicated, formation conditions of shallow gas of Daqing placanticline are good and its environment condition and substance condition are both good. Shallow gas developed three sets of gas combinations, i. e., the lower, the central and the upper. The lower gas combination is K1n2, mainly containing gas to northern placanticline, the central gas combination is K2n3 and it isthe main gas bearing layer in the southern placanticline, the upper gas combination is K2n4 and the gas level is in general. The contribution factors of shallow gas are different. The Xingshugan and Lamadian area are dominated by typical crude associated gas, coming from next overlying reservoirs. Punan area is characterized by crude oil bacterial degraded gas, Oil-type gas containing heavy hydrocarbon components. In the Aonan area, it is mixed gas of crude oil bacterial degraded gas and oil-type gas. shallow gas reservoir type of Daqing placanticline are structure natural gas reservoir. Shallow natural gas is mainly affected by crude oil and gas source rock, structure, reservoir and fracture.