The Simulation Of Tectonic Stress Field And The Prediction Of Tectonic Fracture In Ordovician In Tazhong Area, Tarim Basin

By now, several oil-gas fields have been founded in Tazhong area which is located inthe central uplift of Tarim basin. It shows that there are huge potentials of petroleumresources and exploration prospects in Tazhong area. As a result, by simulating thetectonic stress fields of the Ordovician strata with thin plate-bending trend surface methodand 3-D finite element method, this paper is to predict the fracture zones in Griffith'srupture criterion and thus to point out some new favorable zones to SINOPEC for the nextexploration in Tazhong area.Based on the former achievements, the author made full use of the ancient and recentstructure map of T₇⁰, T₇⁴ and T₈¹ boundaries of key stratum and simulated the Ordoviciantectonic stress field in Tazhong area with the well data, the rock mechanical test and rocktensile strength test. The effective tensile stress fields of Caledonian (T₇⁴), Hercynian (T₇⁰,T₇⁴) and recent (T₇⁰, T₇⁴) were simulated in thin plate-bending trend surface method. Andthe recent principal tensile stress fields and effective tensile stress fields of upper andlower Ordovician were simulated in 3-D finite element method. In this paper, thedistribution regularities of these stress fields are described separately. It also makes acomparison between the two methods.Based on Griffith's rupture criterion, according to the effective tensile stress fields,using the development criteria of second or third fracture, this paper separately predictsthe favorable fracture zones of upper and lower Ordovician in Tazhong area. The statistics,which were obtained from fracture linear density of single well and the locations ofoil-gas wells, testifies that the tectonic fracture zones which were predicted by using 3-Dfinite element method basically agrees with the actual facture areas in Tazhong area. Italso shows that the oil-gas reservoirs are mostly located in the tectonic stress fields withhigh volume.According to the prediction and the evaluation of reservoir in Tazhong area, thispaper suggests that there should be 4 important favorable zones for next exploration toSINOPEC, which are the following areas: Z1-Z12-Tz23-Tz37 area;TB2 area;Z3-Tz3area and the north part of Ka4 block, including the GuCheng uplift.Tectonic stress field is an important factor dominating the developement of fractureand having an impact on the formation of cracking reservoir. It can predict the fracturezones and point out the favorable areas of reservoir by using numerical simulation oftectonic stress field. It is also a new clew and a new method for further exploration intarget area.