Coal-formed gas reservoirs have been found in several depressions in Bohai Bay Basin. The gas was mainly generated by the Carboniferous-Permian coal measures, which are good source rocks. The exploration of coal-formed gas has a broad prospect. The main reservoirs of the coal-formed gas are Ordovician, Carboniferous-Permian, and Paleogene stratum. Coal-formed gas in the Bohai Bay Basin is chiefly composed of hydrocarbon gases. The percentage content of carbon dioxide is more than that of the nitrogen gas. The stable carbon isotope values of the hydrocarbon gases of different depressions and different reservoirs usually reversed. The reversed values of gas samples account for 52.1% of all the samples. Reversion values of the carbon isotope are mainly because of the mixing of gases from same source rocks but with different maturity. Among the three main reservoirs, coal-formed gas preserved in Paleogene stratum has the heaviest carbon isotope, the second is the gas in Carboniferous-Permian stratum, and the Ordovician gas possesses the lightest carbon isotope. Based on the analysis of the characteristics of carbon isotope of hydrocarbon gases in well Qishen-1 and the distribution of the Carboniferous-Permian coal measures, the gas of the well is derived from the high-matured Carboniferous-Permian coal measures.
ChengK.M.XiongY. and ZhangX.B., 2002. An approach to the timing formation for primary oil pools of Ordovician system in Kongxi buried hill. Petroleum Exploration and Development29(4), 16–20.
2.
DaiJ.X., 1988. An approach on gases derived from coal measures in Jizhong Depression. Experimental Petroleum Geology10(2), 189–195.
3.
DaiJ.X., 1990. A berif discussion on the problem of the geneses of the carbon isotopic series reversal in organic alkane gases. Natural Gas Industry10(6), 15–20.
4.
DaiJ.X.PeiX.G. and QiH.F., 1992. China Natural Gas Geology. Petroleum Industry Press, Beijing, pp. 40–43.
5.
DaiJ.X.XiaX.Y.QinS.F. and ZhaoJ.Z., 2003. Causation of partly reversed orders of δ13C in biogenic alkane gas in China. Oil & Gas Geology24(1), 1–6.
6.
DaiJ.X.NiY.Y.LiJ.HuG.Y. and ZhuG.Y., 2008. Carbon isotope types and significances of alkane gases from Junggar Basin and Tarim Basin. XinJiang Petroleum Geology29(4), 403–410.
7.
DaiJ.X.XiaX.Y. and HongF., 2002. Natural gas geology accelerated the growth of natural gas reserve in large scale in China. Xinjiang Petroleum Geology23(5), 357–365.
8.
DaiJ.X.QinS.F.TaoS.Z.ZhuG.Y. and MiJ.K., 2005. Developing trend of natural gas industry and the significance progress on natural gas geological theories in China. Natural Gas Geoscience16(2), 127–142.
9.
DaiJ.X., 2007. Potential areas for coal-formed gas exploration in China. Petroleum Exploration and Development34(6), 641–645.
10.
DaiJ.X.HuG.Y.NiY.Y.LiJ.LuoX.YangC.HuA.P., and ZhouQ.H., 2009. Natural gas accumulation in Eastern China. Energy Exploration & Exploitation27(4), 225–259.
11.
FengJ.H.RenZ.L.CuiJ.P.RenL.Y.MaW.M. and SunM.L., 2003. Analysis on gas-source rock correlation in Duqiaobai area of Dongpu Depression. Acta Sedimentologica Sinica21(2), 350–354.
12.
GangW.Z.GaoG.HaoS.S.HuangZ.L. and ZhuL., 1997. Carbon isotope of ethane applied in the analyses of genetic types of natural gas. Experimental Petroleum Geology19(2), 164–167.
13.
GuoJ.Y.YuX.M.LiJ.WangD. L.CuiH. Y. and LiZ. S., 2009. Gas source of Qishen-1 well in Qikou Sag. Natural Gas Geoscience20 (3), 392–399.
14.
HeX.L.WangX.L.WuX.L.WangY.S. and JiangY.J., 2002. Genesis type of natural gas in Dongpu Depression and its range of profitability of exploration. Fault-Block Oil & Gas Field, 9(6), 25–28.
15.
HuangZ.J. and LiX.F., 2001. Geochemical characteristics and natural gas sources of Bozhong Depression, Bohai Bay Basin. Petroleum Exploration and Development28(3), 17–21.
16.
JiaC.S. and RaoD., 2007. Discussion on origin of deep mixed natural gas reservoirs of Machang structure, Dongpu Depression. Petroleum Geology and Recovery Efficiency14(1), 32–35.
17.
JiangX.R.LuoX.P. and ZhengS.Q., 2005. New evidence for the formation simulation of natural gas and coal-type gas in the Dongpu Sag. J Mineral Petrol25(2), 110–113.
18.
JiangY.L.LiZ.L.TanY.M.ChangZ.H. and ZhuoQ.G., 2008. Research on history of gas migration and accumulation in fault basin: Taking Wen 23 gas field of Dongpu Depression as an example. Acta Petroleum Sinica29(5), 633–638.
19.
JiaoW.W.ZhangS.C. and SunY.Z., 2009. Geochemical characteristics of source rocks from jiyang depression. World Journal of Engineering6(1), 170–173
20.
JinQ.SongG. Q.LiangH.B.ChengF.Q. and WangL., 2009. Characteristics of Carboniferous-Permian coal –derived gas in the Bohai Bay Basin and their implication to exploration potential. Acta Geologica Sinica83(6), 861–867.
21.
JinQ.SongG.Q. and WangL., 2009. Generation models of Carboniferous-Permian coal-derived gas in Shengli oilfield. Petroleum Exploration and Development36(3), 358–364.
22.
LiangS.Z.RenT.K.ZengX.Y.LiangY.H.BaiJ.H. and SongX.Y., 2005. Exploration direction and target of natural gas in the Bohai Bay Basin. Petroleum Geology & Experiment27(6), 565–569.
23.
LiaoQ.J.YuX.M.HeY.M. and LiuX.J., 2003. The characteristics and resource potential of coal-bearing formations in Upper Paleozoic in Dagang Oilfield. Natural Gas Geoscience14(4), 250–253.
24.
LinW.LiZ.LiJ.Y. and XuX.Y., 2007. Genetic types and distribution pattern of natural gases in Gubei buried-hills, Jiyang Depression. Oil & Gas Geology28(3), 419–426.
25.
LiX.Q.LuS.Q. and DuX.B., 2008a. Natural gas exploration of Jiyang Depression viewed from Dongpu Depression. Geological Science and Technology Information27(2), 43–48.
26.
LiZ.L.JiangY.L. and LuX.S., 2008b. Geochemical characteristics of gas accumulation in HuBuzhai gas field, Dongpu Depression. Journal of Southwest Petroleum University (Science & Technology Edition)30(2), 56–60.
27.
PengC.S., 2005. The pool-forming condition and character of coal-derived gas in Gubei deeply buried hill of Jiyang Depression. Periodical of Ocean University of China35(4), 670–676.
28.
QinJ.Z.GuoS.Z. and WangD.L., 1991. Geochemical characteritics of Suqiao coal-derived gas field and their contrast. Natural Gas Industry11(5), 21–26.
29.
SunY.Z.PüttmannW.KalkreuthW. and HorsfieldB., 2002. Petrologic and geochemical characteristics of Seam 9–3 and Seam 2, Xingtai Coalfield, Northern China. International Journal of Coal Geology49, 251–262.
30.
SunY.Z.JiaoW.W.ZhangS.C. and QinS.J., 2009. Gold enrichment mechanism in crude oils and source rocks in Jiyang Depression. Energy Exploration & Exploitation27(2), 133–142.
31.
WangL.JinQ.WanC.L.HuX.Q. and WangX.H., 2008. Origin of natural gas and formation conditions of gas reservoir in Boshen 6 buried-hill. Journal of Xi'an Shiyou University (Natural Science Edition)23(1), 1–11.
32.
WangS.Q., 1994. Geochemical characteristics of Jurassic-Sinian natural gas in Sichuan Basin. Natural gas Industry14(6), 1–5.
33.
WenZ.G.TangY.J.SongH.X.XuY.H. and LiF.P., 2005. Composition and origin of natural gases in central Bohai Sea area, China. Petroleum Exploration and Development32(4), 111–113.
34.
WuY.P. and YangC.Y., 2002. Ordovician Buried Hill in North Bohai Bay Basin. Geological Publishing House, Beijing, pp. 280–290.
35.
WuY. P. and YuX.M., 2003. Natural gas resource potential and the strategy of exploration and development in Huanghua Depression. Natural Gas Geology14(4), 235–239.
36.
YangC.Y.ZhouZ.L. and ZhouJ.S., 2000. Petroleum system and petroleum exploration in Qikou Sag. Petroleum Explorationist5(3), 64–70.
37.
YinL.J.ZhangJ.G.WuH.N.QinF. and XiangX.Y., 2007. Accumulating characteristic of Upper Paleozoic coal-genetic gas pool of well Gubeigu-1. Journal of Northwest University (Natural Science Edition)37(1), 86–90.
38.
ZengF.G. and ChengK.M., 1998. Genesis of coal-generated oil in well Konggu-4 in Huanghua Depression. Geology-Geochemistry26(3), 21–26.
39.
ZhuW.L. and GeJ.D., 2001. Gas exploration potential in offshore Bohai Bay Basin. Acta Petroleum Sinica22(2), 8–13.
