Research On Structures And Its Relations To Hydrocarbon In Machang Region, Dongpu Sag

Machang area is located in the south of the uplift belt of Dongpu sag. The high precision 3-D acquisition zone is to the east of Huanghe River. Machang area can be divided into three structural parts: Machang structural zone, Gegangji south subsag and Sanchunji structural zone.The buried hill belt of Machang area can be taken into four typical structural styles: fault terrace-horst fault block buried hill, asymmetric half-horst fault block buried hill, tilt-asymmetric half-horst fault block buried hill and high-amplitude asymmetric half-horst fault block buried hill. In the basic of buried-hill trap, we predict that this area can form 3 types of hydrocarbon reservoir: paleo-storage of mixed born and paleo plug, paleo-storage of mixed born and new plug, paleo-storage of newborn and new plug. These three types of buried-hill trap were arranged in a crisscross pattern, the upper and lower parts closed pack. Hydrocarbon accumulating zone may have possibilities to form.The oil-control effort of Machang area was similar to Changdong fault system; it was the barrier to the hydrocarbon. Machang fault system with the rotate tilted formation composed the roof hydrocarbon reservoir, a brush shaped. For local stress of Madong faults system changed to loose, it became the most important hydrocarbon transport channel. The hydrocarbon reservoir of Machang area was fault-block type, the main features were: horst, fault terrace (antithetic and concurrent) and reverse roof fault-block trap.The studying zone of Machang had two main transverse structural transfer zones, Line 500 and Line 1200; two secondary transfer zones, Line 900 and Line 1400. They were almost accordant overlap transition structures. The relations between the transition structures and the hydrocarbon were: forming the structural and stratigraphic trap, controlling the ancestral river-paleogeography, sedimentary lightfaces, reservoir rock and source rock distribution, then finally control the hydrocarbon. The most available type is anticline transfer zone which superpose syncline co-rotating parallel, the enrichment of hydrocarbon is high.The correlative folds developed in Machang area extensional fault were mainly vertical fold, then oblique fold. The styles of the fold were fault-bend fold, fault-propagation fold, transfer zone fold, big scale balanced fold and complex fold. Extensional fold (anticline) was the most important hydrocarbon trap in extensional basin. Because of the characteristics of the extensional anticline, it can control the distribution of sedimentary faces zone, accelerate hydrocarbon migration. High productivity enrichment concourse can be formed by structural trap superposed structural-lithology-formation complex trap.By restudying on the formation and structure, we found at the east-northeast-Madong fault terrace region, still exist many fault-block hydrocarbon reservoir. The hydrocarbon formation embedded suitable, single well production was high, still had exploration potential. The favorable zones were: paleo buried hill zones, Madong fault terrace zones, transfer zones and extensional fold zones.