Tectonic Evolution Of The Ancient Buried Hill And Controls Of Reservois And Hydrocarbon Accumulation In Xinhe-Sandaoqiao Area Of The Northwest Of Tarim Basin

Xinhe sandaoqiao area is located in the northwest of Shaya uplift(Tabei uplift)in Tarim Basin,and its structural core is YAKELA fault convex.The Paleozoic YAKELA fault convex is a long-term inherited paleouplift,which is now represented by the superposition of Paleozoic uplift and Mesozoic Cenozoic front slope.The qiaogu 1,qiaogu 3 and Xinghuo 5 et al condensate gas reservoirs have been found in the pre Mesozoic buried hill in Xinhe-sandaoqiao area,which is the key area for Northwest branch of Sinopec to increase reserves and production.At present,the exploration and development of this area is faced with the following problems:(1)Because of the serious denudation of the pre Mesozoic buried hill and the development of igneous rocks in the study area,the age and distribution of the residual strata are not clear,which also affects our correct understanding of the formation and evolution of buried hill structures;(2)There are many types of reservoirs in the study area,such as magmatic rock,metamorphic rock and carbonate rock;The reservoir development law of different rock types and the main controlling factors of high-quality reservoirs in the study area are still unclear;(3)The YAKELA fault uplift is the favorable direction area for the migration of continental oil and gas in Kuqa in the north and marine oil and gas in the south.There are differences in the accumulation stages and migration paths of marine and continental oil and gas in the study area.Therefore,it is necessary to clarify the charging and distribution range of oil and gas from different sources,On the basis of the research results,the exploration target evaluation of the study area is carried out.In order to solve the above problems,guided by the theory of stratigraphy and structural geology,this paper uses U-Pb isotopic age to define the age of Presinian buried hill strata,and finds out the distribution law of ancient buried hill strata through fine interpretation of seismic data;We analyzed the formation and evolution process of buried hill in the study area used 3D seismic data and well data combined with regional geological research.And we also discussed the control of buried hill structural evolution on hydrocarbon charging and accumulation.The results in the research as follows.(1)In the paper,zircon U-Pb isotopic dating of 7 core samples from 6 wells is used to determine the age of different pre Sinian strata in this area,and the development sequence of pre Sinian strata is established.The granite in the study area was formed in the early Proterozoic and experienced metamorphism in the middle and late Paleoproterozoic(1850 ?1791ma)and magmatism in the early Neoproterozoic(879 ± 4m A).The buried hill strata in qiaogu-1 well area are deposited on the crystal of Early Proterozoic granite and a set of strata before the deposition of Aksu group.The minimum concordant age of three detrital zircon samples is 1522 ± 16 m A,indicating that the sedimentary or diagenetic age should not be earlier than that of Middle Proterozoic(1522 ± 16 m A).The metamorphic strata in Xinghuo 1well area are equivalent to Aksu group of Qingbaikou system,and their sedimentary or diagenetic age is not earlier than 776 ma.(2)Through stratigraphic correlation and 3D seismic comprehensive interpretation,the paleogeological map of pre Mesozoic buried hill in Xinhe sandaoqiao area is compiled.The results show that the pre Mesozoic buried hill in the study area is a ne uplifted asymmetric anticline,the high part is the pre Sinian basement,and the strata on both sides are successively renewed.The Sinian Ordovician ring basement is distributed in the southwest southeast direction,the Sinian Cambrian system is mainly remained in the northeast direction,and the Permian igneous rocks are developed in the northwest.The age of the felsite in Xinghuo 3 well is 294 ± 10 Ma,which represents the latest age of Permian magmatic eruption in this area.(3)The analysis of structural characteristics shows that the buried hill in Xinhe sandaoqiao area has experienced four evolution stages.The first stage is the Sinian Paleozoic carbonate sedimentary formation stage,that is,the formation stage of the material basis of the ancient buried hill;the second stage is the formation stage of the compression uplift and the initial structure pattern of the buried hill from the late Caledonian to the Early Hercynian;the third stage is the formation stage of the thrust uplift and the structure pattern of the buried hill in the late Hercynian;the fourth stage is the rapid burial stage since the Mesozoic and Cenozoic.(4)There are many types of rock reservoirs in the buried hill of Xinhe sandaoqiao area,including carbonate,metamorphic rock and magmatic rock.Dolomite reservoirs is mainly developed in Sinian and Cambrian this area.The porosity of carbonate reservoirs in Xinhe sandaoqiao area is poor,and fractures and dissolution holes are the main types of reservoir space.The formation of high-quality reservoirs is controlled by dolomitization,weathering crust karst and fracture.The reservoirs of magmatic rocks in Xinhe sandaoqiao area are mainly fractures,and the high-quality reservoirs are controlled by paleogeomorphology and faulting.(5)The study of oil and gas geochemistry shows that the distribution of oil and gas from different marine and continental sources in Xinhe-sandaoqiao area is controlled by the geological structure of pre Mesozoic.The core of pre Mesozoic fault ridge is the boundary,the south is the marine facies,and the north is the continental facies.The crude oil from qiaogu 1,qiaogu 102 and qiaogu 3 wells are different in physical properties(waxy and sulfur-containing),light hydrocarbon composition and steroidal and terpane biomarkers.The crude oils from qiaogu 1 and qiaogu 102 wells are characterized by relatively low wax and high sulfur.In terms of crude oil geochemistry,the ratio of PR / pH is relatively low,and the abundance of c19-c21 tricyclic terpanes is relatively high,with C23 as the main peak and rich in sulfur fluorene.The correlation diagrams of PR / nc17 and pH / nc18 show that they were formed in reducing environment,which is marine crude oil characteristics;the crude oils from qiaogu 3 and Xinghuo 1 wells are on the contrary,showing continental crude oil characteristics Sign.(6)The study of hydrocarbon accumulation shows that the Xinhe sandaoqiao area has the characteristics of multi-stage charging and late hydrocarbon accumulation.The paleostructural map of the top surface of the pre Mesozoic buried hill shows the favorable migration and accumulation areas of hydrocarbon charging in different periods.By comparing the paleostructural morphology in different periods,it can be found that the buried hill has experienced multi-stage structural adjustment evolution and the complex process of hydrocarbon charging destruction adjustment accumulation,The multi-stage adjustment of buried hill paleostructure not only controls the development of different types of reservoirs,but also has a significant impact on oil and gas migration and accumulation.