Study On Distribution Of Source Rock Of Ordovician In Tanggubasi Sag And Its Surrounding Region

Tanggubasi Sag lies between Tazhong uplift and Tanan uplift, in Tarim Basin, is about 20 thousands km2. Ordovician system is main hydrocarbon reservoir in Tarim Basin,and it is main constituent sequence also. Ordovician system of Tanggubasi Sag and it's Surrounding Region is composed of shallow water tableland's carbonate rock and clastic rock . Prospect of earlier days approves, this area have under Palaeozoic erathem's Source rock or not will restraint oil and gas exploration activity.This research's focus is Tanggubasi Sag, contains hetian, tazhong, manjiaer surrounding region. On the base of phase sequence method, by use of outcrop exploration, and well's data, the seismic sequences are divided and correlated, and on the base of seismic sequence interpretation, we compile strata depositional isopach map, original basin section, and use well's data, filled formation thickness of slope break to depressed area, compiles palaeobathymetric map, analyzes depositional environment , rate of sedimentation and seismic facies, builds develop model of source rock of Ordovician in Tanggubasi Sag, and for the purpose to Middle-Upper Ordovician's source rock, analyzes it's rate of sedimentation and content of TOC, The results and cognitions are as follows:(1) Through original basin, Tanggubasi Sag is foreland sag which formed in the end of Early Ordovician. During Early Ordovician, it is open platform, and Late Ordovician is foreland deep water sag.(2) Through filled formation thickness of slope break to depressed area of S13, and platform is sea level possibly, compiles palaeobathymetric map. During Late Ordovician, Tanggubasi Sag is half deep water-deep water, there are sag in the platform, foreland deep water sag, restricted platform, open sea shelf facies.(3) Use sequence thickness and content of TOC of TZ29, TC1, sequence thickness and content of toc is inverse relation, rate of sedimentation controls source of rock.(4) Seismic analyze disclosure the probably facies belt of source rock in Middle-Upper Ordovician is weak-middle amplitude continuously seismic facies in the south of tazhong to north of Tanggubasi sag and manjiaer sag.(5) Use the palaeobathymetric map to certain the deep water area, and sequence thickness and content of TOC of TC1, TZ29, sequence thickness of S10, S11, obtains the TOC's planimetric map. The TOC of rock core and debris of TC1 is different obviously, so we use two methods to deduce the source rock, and judge that the method of crop restrict is feasible, the rock core's test resul is correct.(6) The main depositional substance of Tanggubasi sag Middle-Upper Ordovician is from east by south of sag. Middle-west of Tazhong restricted platform's gradient break to south slope,the area of TB2-Z3 to north is middle-bad source rock. TZ12 to north in manjiaer sag is good to source rock.