In the last ten years, with important discoveries from oil and gas exploration in the Dabashan foreland depression belt in the borderland between Shanxi and Sichuan provinces, the relationship between the formation an...In the last ten years, with important discoveries from oil and gas exploration in the Dabashan foreland depression belt in the borderland between Shanxi and Sichuan provinces, the relationship between the formation and evolution of, and hydrocarbon accumulation in, this foreland thrust belt from the viewpoint of basin and oil and gas exploration has been studied. At the same time, there has been little research on the origin of fluids within the belt. Based on geochemical system analysis including Z values denoting salinity and research on δ13C, δ18O and S7Sr/S6Sr isotopes in the host rocks and veins, the origin of paleofluids in the foreland thrust belt is considered. There are four principal kinds of paleofluid, including deep mantle-derived, sedimentary, mixed and meteoric. For the deep mantle-derived fluid, the δ13C is generally less than -5.0‰PDB, δ18O less than -10.0‰PDB, Z value less than 110 and 87Sr/86Sr less than 0.70600; the sedimentary fluid is mainly marine carbonate- derived, with the δ13C generally more than -2.0‰PDB, 18δO less than -10.0‰PDB, Z value more than 120 and STSr/S6Sr ranging from 0.70800 to 0.71000; the mixed fluid consists mainly of marine carbonate fluid （including possibly a little mantle-derived fluid or meteoric water）, with the j13C generally ranging from -2.0‰ to -8.0‰PDB, δ18O from -10.0‰ to -18.0‰ PDB, Z value from 105 to 120 and 87Sr/86Sr from 0.70800 to 0.71000; the atmospheric fluid consists mainly of meteoric water, with the δ13C generally ranging from 0.0‰ to -10.0‰PDB, δ18O less than -8.0%rPDB, Z value less than 110 and 87Sr/86Sr more than 0.71000. The Chengkou fault belt encompasses the most complex origins, including all four types of paleofluid; the Zhenba and Pingba fault belts and stable areas contain a simple paleofluid mainly of sedimentary type; the Jimingsi fault belt contains mainly sedimentary and mixed fluids, both consisting of sedimentary fluid and meteoric water. Jurassic rocks of the foreland depression belt contain mainly meteoric fluid.展开更多
Under the joint action of gypsum-salt rocks and faults,fluid evolution process is complicated in the northern Tuzimazha,Kuqa Depression,Tarim Basin.In the past,however,the oil and gas distribution rules in this area w...Under the joint action of gypsum-salt rocks and faults,fluid evolution process is complicated in the northern Tuzimazha,Kuqa Depression,Tarim Basin.In the past,however,the oil and gas distribution rules in this area were less studied,so the related understanding was insufficient.In this paper,the reservoirs in Well Block Tubei 1 were analyzed by means of fluid inclusion and quantitative grain fluorescence(QGF)techniques.Based on tectonic evolution history,burial history,thermal history and hydrocarbon generation history,the paleofluid evolution process in this area was reproduced.It is shown that the well block experienced hydrocarbon charge in two periods.The first period is the earlyemiddle stage(16-9 Ma)of Miocene Kangcun Fm(N_(1-2)k),when it was charged with oil,with the corresponding characteristics of yellow and whiteeyellow fluid inclusion fluorescence and the QGF Index higher than 4,indicating that there were paleo-oil reservoirs at the early stage of the reservoirs.And at the late stage,the fluids that were accumulated at the early stage escaped because the gypsum-salt rocks were cut by faults,and bitumen remained in the reservoirs.It is also the evidence for the escaping of the early charged oil that the total scanning fluorescence(TSF)of the hydrocarbon adsorbed to the surface of the current reservoirs is generally unimodal.The second period is the late stage(about 3 Ma)of Pliocene Kuqa Fm(N_(2)k),when the natural gas and light oil charging occurred.Correspondingly,there are two inclusions,i.e.black gaseous hydrocarbon inclusion and blue fluorescence inclusion located along the edge of the quartz grains.At this stage,the gypsum-salt caprocks deepened and their sealing capacity was recovered due to a strong plastic flow.Moreover,the trap was uplifted violently under the effect of Himalaya orogeny,and a large amount of natural gas and a little light oil were accumulated.展开更多
基金supported by the National Basic Research Project("973" Project,Grant No. 2006CB202305) and SINOPEC
文摘In the last ten years, with important discoveries from oil and gas exploration in the Dabashan foreland depression belt in the borderland between Shanxi and Sichuan provinces, the relationship between the formation and evolution of, and hydrocarbon accumulation in, this foreland thrust belt from the viewpoint of basin and oil and gas exploration has been studied. At the same time, there has been little research on the origin of fluids within the belt. Based on geochemical system analysis including Z values denoting salinity and research on δ13C, δ18O and S7Sr/S6Sr isotopes in the host rocks and veins, the origin of paleofluids in the foreland thrust belt is considered. There are four principal kinds of paleofluid, including deep mantle-derived, sedimentary, mixed and meteoric. For the deep mantle-derived fluid, the δ13C is generally less than -5.0‰PDB, δ18O less than -10.0‰PDB, Z value less than 110 and 87Sr/86Sr less than 0.70600; the sedimentary fluid is mainly marine carbonate- derived, with the δ13C generally more than -2.0‰PDB, 18δO less than -10.0‰PDB, Z value more than 120 and STSr/S6Sr ranging from 0.70800 to 0.71000; the mixed fluid consists mainly of marine carbonate fluid （including possibly a little mantle-derived fluid or meteoric water）, with the j13C generally ranging from -2.0‰ to -8.0‰PDB, δ18O from -10.0‰ to -18.0‰ PDB, Z value from 105 to 120 and 87Sr/86Sr from 0.70800 to 0.71000; the atmospheric fluid consists mainly of meteoric water, with the δ13C generally ranging from 0.0‰ to -10.0‰PDB, δ18O less than -8.0%rPDB, Z value less than 110 and 87Sr/86Sr more than 0.71000. The Chengkou fault belt encompasses the most complex origins, including all four types of paleofluid; the Zhenba and Pingba fault belts and stable areas contain a simple paleofluid mainly of sedimentary type; the Jimingsi fault belt contains mainly sedimentary and mixed fluids, both consisting of sedimentary fluid and meteoric water. Jurassic rocks of the foreland depression belt contain mainly meteoric fluid.
基金Project supported by National Major Oil and Gas Project(Grant No.2011ZX05003)CNPC Technological Development Project(Grant No.2014B-04)。
文摘Under the joint action of gypsum-salt rocks and faults,fluid evolution process is complicated in the northern Tuzimazha,Kuqa Depression,Tarim Basin.In the past,however,the oil and gas distribution rules in this area were less studied,so the related understanding was insufficient.In this paper,the reservoirs in Well Block Tubei 1 were analyzed by means of fluid inclusion and quantitative grain fluorescence(QGF)techniques.Based on tectonic evolution history,burial history,thermal history and hydrocarbon generation history,the paleofluid evolution process in this area was reproduced.It is shown that the well block experienced hydrocarbon charge in two periods.The first period is the earlyemiddle stage(16-9 Ma)of Miocene Kangcun Fm(N_(1-2)k),when it was charged with oil,with the corresponding characteristics of yellow and whiteeyellow fluid inclusion fluorescence and the QGF Index higher than 4,indicating that there were paleo-oil reservoirs at the early stage of the reservoirs.And at the late stage,the fluids that were accumulated at the early stage escaped because the gypsum-salt rocks were cut by faults,and bitumen remained in the reservoirs.It is also the evidence for the escaping of the early charged oil that the total scanning fluorescence(TSF)of the hydrocarbon adsorbed to the surface of the current reservoirs is generally unimodal.The second period is the late stage(about 3 Ma)of Pliocene Kuqa Fm(N_(2)k),when the natural gas and light oil charging occurred.Correspondingly,there are two inclusions,i.e.black gaseous hydrocarbon inclusion and blue fluorescence inclusion located along the edge of the quartz grains.At this stage,the gypsum-salt caprocks deepened and their sealing capacity was recovered due to a strong plastic flow.Moreover,the trap was uplifted violently under the effect of Himalaya orogeny,and a large amount of natural gas and a little light oil were accumulated.
