Well Gaotan 1 was tested a high yield oil and gas flow of more than 1 000 m^3 a day in the Cretaceous Qingshuihe Formation,marking a major breakthrough in the lower assemblage of the southern margin of Junggar Basin. ...Well Gaotan 1 was tested a high yield oil and gas flow of more than 1 000 m^3 a day in the Cretaceous Qingshuihe Formation,marking a major breakthrough in the lower assemblage of the southern margin of Junggar Basin. The lower assemblage in the southern margin of the Junggar Basin has favorable geological conditions for forming large Petroleum fields, including:(1) Multiple sets of source rocks, of which the Jurassic and Permian are the main source rocks, with a large source kitchen.(2) Multiple sets of effective reservoirs,namely Cretaceous Qingshuihe Formation, Jurassic Toutunhe Formation and the Khalza Formation etc.(3) Regional thick mudstone caprock of Cretaceous Tugulu Group, generally with abnormally high pressure and good sealing ability.(4) Giant structural traps and litho-stratigraphic traps are developed. The northern slope also has the conditions for large-scale litho-stratigraphic traps.(5) Static elements such as source rocks, reservoirs and caprocks are well matched, and the dynamic evolution is suitable for large oil and gas accumulation. The lower assemblage of the southern margin of the Junggar Basin has three favorable exploration directions, the Sikeshu Sag in the west part, the large structures in the middle and eastern part, and the northern slope.展开更多
Based on drilling cores, well logging and seismic data, source rocks and reservoirs are evaluated;and the natural gas genesis is identified through the analysis of natural gas isotopes, components and fluid inclusions...Based on drilling cores, well logging and seismic data, source rocks and reservoirs are evaluated;and the natural gas genesis is identified through the analysis of natural gas isotopes, components and fluid inclusions, to study the gas accumulation conditions of the gypsum salt rock related strata of the Ordovician lower assemblage in Ordos Basin.(1) The natural gas from Ordovician lower assemblage is high thermal evolution dry gas from marine source rock, characterized by relatively light δ^(13)C value of methane and heavy δ^(13)C value of ethane. The natural gas is identified as gas cracking from crude oil according to component analysis. Thermochemical sulfate reduction(TSR) reaction has happened between the hydrocarbon fluid and sulfate as sulfur crystals are found in the cores, hydrogen sulfide is found in the natural gas, and hydrocarbon and hydrogen sulfide fluid inclusions are widespread in secondary minerals.(2) Around the gypsum-salt lows, argillaceous rocks are extensive in the Ordovician lower assemblage, reaching a cumulative thickness of 20–80 m. The effective source rocks include argillaceous rock rich in organic laminae, algal clump and algal dolomite. Analysis shows that the source rocks have a dominant TOC of 0.1%–0.5%, 0.31% on average and 3.24% at maximum. The source rocks have an average TOC of 0.58% after recovered through organic acid salt method, indicating the source rocks have high hydrocarbon supply potential.(3) In the sedimentary period, the palaeo-uplift controlled the distribution of reservoirs. The inherited secondary palaeo-uplift in Wushenqi–Jingbian east of the central palaeo-uplift and the low uplift formed by thick salt rocks near Shenmu–Zizhou area controlled the distribution of penecontemporaneous grain shoal dolomite reservoirs. The salinization sedimentary environment of gypsum salt rock can promote the development of reservoir. There are three types of dolomite reservoirs, the one with intercrystalline pore, with dissolution pore, and with fracture;intercrystalline and dissolution pores are main reservoir spaces.(4) There are two types of cap rocks, namely tight carbonate rock and gypsum-salt rock, constituting two types of source-reservoir-cap assemblages respectively. The general accumulation model is characterized by marine source rock supplying hydrocarbon, beach facies limy dolomite reservoir, small fractures acting as migration pathways, and structural-lithologic traps as accumulation zones.(5) The third and fourth members of Majiagou Formation are major target layers in the lower assemblage. The Wushengqi–Jingbian secondary paleo-uplift area and Shenmu–Zizhou low uplift are dolomite and limestone transition zone, there develops tight limestone to the east of the uplift zone, which is conducive to the formation of gas reservoir sealed by lithology in the updip. Two risk exploration wells drilled recently have encouraging results, indicating that the two uplift zones are important prospects.展开更多
In view of the difficulties in the study of lithofacies paleogeography and the low reliability of the distribution range of sedimentary sand bodies in the prototype basin caused by less deep drilling, complex seismic ...In view of the difficulties in the study of lithofacies paleogeography and the low reliability of the distribution range of sedimentary sand bodies in the prototype basin caused by less deep drilling, complex seismic imaging and low degree of exploration in the southern margin of Junggar Basin, NW China. A new method based on the source to sink idea was used to restore lithofacies paleogeography and predict glutenite distribution. In the restoration, apatite fission track age was used to define range and uplift time of macro-provenance;the range of provenance area and the migration process of lake shoreline were restored based on the quantitative relationship between gravel diameter and transportation distance, tectonic shortening and other geological parameters;drilling cores and field outcrop sedimentary structures were analyzed, and a series of maps of lithofacies paleogeographic evolution and distribution range of glutenite bodies were compiled. It is concluded that from Early Jurassic to Early Cretaceous, in the southern margin of Junggar Basin, the provenance area gradually expanded from south to north, the lake basin expanded, shrunk and expanded, and the paleoclimate changed from humid to drought to humid. The western section always had proximal fan delta deposits from the southern ancient Tianshan provenance developed, and in the middle and eastern sections, the provenance areas evolved from far source to near source, mainly river-delta, braided delta, fan delta and other sediments developed. The boundary between provenance areas of the western and middle sections is speculated to be Hongche fault zone. In an angle open to the northwest with the current basin edge line, the restored ancient lake shoreline controlled the heterogeneity of reservoirs in the delta plain belt and delta front belt on its both sides. The ancient lake shoreline, current stratigraphic denudation line and current basin margin line limit the types and scope of favorable reservoirs.This understanding provides an important geological basis for oil and gas exploration in the deep lower source-reservoir assemblage at the southern margin of Junggar Basin.展开更多
基金Supported by the PetroChina Exploration&Production Company Project(kt2018-03-01)
文摘Well Gaotan 1 was tested a high yield oil and gas flow of more than 1 000 m^3 a day in the Cretaceous Qingshuihe Formation,marking a major breakthrough in the lower assemblage of the southern margin of Junggar Basin. The lower assemblage in the southern margin of the Junggar Basin has favorable geological conditions for forming large Petroleum fields, including:(1) Multiple sets of source rocks, of which the Jurassic and Permian are the main source rocks, with a large source kitchen.(2) Multiple sets of effective reservoirs,namely Cretaceous Qingshuihe Formation, Jurassic Toutunhe Formation and the Khalza Formation etc.(3) Regional thick mudstone caprock of Cretaceous Tugulu Group, generally with abnormally high pressure and good sealing ability.(4) Giant structural traps and litho-stratigraphic traps are developed. The northern slope also has the conditions for large-scale litho-stratigraphic traps.(5) Static elements such as source rocks, reservoirs and caprocks are well matched, and the dynamic evolution is suitable for large oil and gas accumulation. The lower assemblage of the southern margin of the Junggar Basin has three favorable exploration directions, the Sikeshu Sag in the west part, the large structures in the middle and eastern part, and the northern slope.
基金Supported by the National Key R&D Program of China(2017YFC0603106)National Petroleum Science and Technology Major Project(2016ZX05004-006)Science and Technology Project of PetroChina Exploration and Production Company(kt20180401)。
文摘Based on drilling cores, well logging and seismic data, source rocks and reservoirs are evaluated;and the natural gas genesis is identified through the analysis of natural gas isotopes, components and fluid inclusions, to study the gas accumulation conditions of the gypsum salt rock related strata of the Ordovician lower assemblage in Ordos Basin.(1) The natural gas from Ordovician lower assemblage is high thermal evolution dry gas from marine source rock, characterized by relatively light δ^(13)C value of methane and heavy δ^(13)C value of ethane. The natural gas is identified as gas cracking from crude oil according to component analysis. Thermochemical sulfate reduction(TSR) reaction has happened between the hydrocarbon fluid and sulfate as sulfur crystals are found in the cores, hydrogen sulfide is found in the natural gas, and hydrocarbon and hydrogen sulfide fluid inclusions are widespread in secondary minerals.(2) Around the gypsum-salt lows, argillaceous rocks are extensive in the Ordovician lower assemblage, reaching a cumulative thickness of 20–80 m. The effective source rocks include argillaceous rock rich in organic laminae, algal clump and algal dolomite. Analysis shows that the source rocks have a dominant TOC of 0.1%–0.5%, 0.31% on average and 3.24% at maximum. The source rocks have an average TOC of 0.58% after recovered through organic acid salt method, indicating the source rocks have high hydrocarbon supply potential.(3) In the sedimentary period, the palaeo-uplift controlled the distribution of reservoirs. The inherited secondary palaeo-uplift in Wushenqi–Jingbian east of the central palaeo-uplift and the low uplift formed by thick salt rocks near Shenmu–Zizhou area controlled the distribution of penecontemporaneous grain shoal dolomite reservoirs. The salinization sedimentary environment of gypsum salt rock can promote the development of reservoir. There are three types of dolomite reservoirs, the one with intercrystalline pore, with dissolution pore, and with fracture;intercrystalline and dissolution pores are main reservoir spaces.(4) There are two types of cap rocks, namely tight carbonate rock and gypsum-salt rock, constituting two types of source-reservoir-cap assemblages respectively. The general accumulation model is characterized by marine source rock supplying hydrocarbon, beach facies limy dolomite reservoir, small fractures acting as migration pathways, and structural-lithologic traps as accumulation zones.(5) The third and fourth members of Majiagou Formation are major target layers in the lower assemblage. The Wushengqi–Jingbian secondary paleo-uplift area and Shenmu–Zizhou low uplift are dolomite and limestone transition zone, there develops tight limestone to the east of the uplift zone, which is conducive to the formation of gas reservoir sealed by lithology in the updip. Two risk exploration wells drilled recently have encouraging results, indicating that the two uplift zones are important prospects.
基金Supported by China National Science and Technology Major Project (2016ZX05003-001)PetroChina Science and Technology Project (2019B-0505,2021DJ0202,2021DJ0302)。
文摘In view of the difficulties in the study of lithofacies paleogeography and the low reliability of the distribution range of sedimentary sand bodies in the prototype basin caused by less deep drilling, complex seismic imaging and low degree of exploration in the southern margin of Junggar Basin, NW China. A new method based on the source to sink idea was used to restore lithofacies paleogeography and predict glutenite distribution. In the restoration, apatite fission track age was used to define range and uplift time of macro-provenance;the range of provenance area and the migration process of lake shoreline were restored based on the quantitative relationship between gravel diameter and transportation distance, tectonic shortening and other geological parameters;drilling cores and field outcrop sedimentary structures were analyzed, and a series of maps of lithofacies paleogeographic evolution and distribution range of glutenite bodies were compiled. It is concluded that from Early Jurassic to Early Cretaceous, in the southern margin of Junggar Basin, the provenance area gradually expanded from south to north, the lake basin expanded, shrunk and expanded, and the paleoclimate changed from humid to drought to humid. The western section always had proximal fan delta deposits from the southern ancient Tianshan provenance developed, and in the middle and eastern sections, the provenance areas evolved from far source to near source, mainly river-delta, braided delta, fan delta and other sediments developed. The boundary between provenance areas of the western and middle sections is speculated to be Hongche fault zone. In an angle open to the northwest with the current basin edge line, the restored ancient lake shoreline controlled the heterogeneity of reservoirs in the delta plain belt and delta front belt on its both sides. The ancient lake shoreline, current stratigraphic denudation line and current basin margin line limit the types and scope of favorable reservoirs.This understanding provides an important geological basis for oil and gas exploration in the deep lower source-reservoir assemblage at the southern margin of Junggar Basin.
