The Causes Of Shallow Layer Gas And Resource Potential Research ,South Changyuan, Daqing

The shallow gas is generally refers the burial depth of natural gas less than 1500m, which characteristics are shallowly burial, lowly cost, quickly effective, small risk and easily exploration development. Its genesis may conclude ,low-mature gas and transitional zone gases,the most important one is. Take biogas for example , people have already discovered that it's easy to generate the biogas in the shallow deposition, but in a long period, people considered that the shallow cover rock quality is deviate, so people think that it's difficult to accumulate massively and did'nt pay attention to the meaning of biogas accumulation , However ,as the exploration and research going on, people realized that under the beneficial geology condition , the biogas not only could generate but also accumulate massively.As the increasingly difficults of petroleum exploration, the significance of shallow gas exploration is increasingly prominent. Statistics indicated that the biogas accumulation of detected was 21.4% of the natural gas reserves in the world. The Songliao basin is the richest oil and gas basin, and also the richest shallow gas basins.Putaohua structure and several structures in south of Placanticline are important oil-bearing structures of Daqing Placanticline ,during the exploration of the late 50 years we have found the exist of shallow gas .,but some accidents often happen during the drilling,such as flusher and well blowout. Along with the well drilling region expansion, the abnormal phenomenons about the shallow gas are more and more clear .It demonstrated this area has great exploration potential, the fundamental research also demonstrated this area is the advantageous target area . But the shallow layer's formation,origin, is unknow, actually the amount of resources and some basic question not yet to reply.This article to write for the purpose of discussing the formation , origin and distribution characteristic by using the natural gas component and the isotope data . According to the hot history ,bury history we can appraisal formation stage , It can provide the basis for reserve condition; On the hydrocarbon source rock qualitative appraisal foundation we can use the element balancing method to provide the amount of resources.1.The reservoir gas in reaserch area of Putaohua Structure Heidimiao are biogas; The reservoir gas in Puxi nosing structure Heidimiao reservoir are mixture of biogas,thermal genetic gas, abiogenic origin gas, Biogas occupie 65% of organic gas, thermal genetic gas is 35%2.The reaserch area N₁ ,N₂, N₃ are good Biogas source rock , and most gases of N₂, N₃ are on the peak stage of biogas generation; N₁ is just after the peak Stage of biogas generation; the contribution of N₁ ,N₂, N₃ to the Heidimiao reservoir Biogenetic gas is very small.3.The peak stage of the reaserch area is main in the last deposit stage of Nenjiangzu , the resources of Biogas is 204.68～438.68×10⁸m³ , and the Contribution of N₁ is 57.38～127.05×10⁸m³, N₂ is 27.13～59.87×10⁸m³, N₃ is 6.23～13.81×10⁸m³ ,the Contribution of N₄, N₅ is very small,and other is Qingshankouzu.