Structural Evolution And Control Action Of Hydrocarbon Of BaChu Bachu Paleo-uplift

Paleo-uplift is the centre of longtime petroleum migration and accumulation,and is the one of primary petroleum-prospecting areas in the central and west of China. Bachu paleo-uplift was found in Tarim Basin in the recent several years.This paper depended on the thought of combining geology and geophysics studies togegher, under condition of the regional geolgy. It was based on the technique of seismic interpretation and the analysis of fault structure which included fault-related fold and strike-slip fault structure and inverted structure. The method of analysis of equilibrium profile was also used to distinguish correctly about the times and period of the formation and evolution of the Bachu paleo-uplift. Through these methods the disconnected horizon and the style of structure deformation can be confirmed by period. The formation, evolution and the activitiy periods of the fault was judged by the factors such as the relationship of fault interpretation in seismic section, grouth fault, disconnected horizon, fault attribute, the variation of displacement of fault and thickness of statum. Then it studied the areal distribution of fault activity by period. Under the interpretation of 2D seismic section the structural stytle of Bachu paleo-uplift was got: compressional structure, strike-slip structure, inverted structure and compound structure. This paper also summarized the trap style in study area such as structrural trap, formation lithology trap and compound trap and so on. It got the new and logical vision of the regional geologic evolution by the analysis of evolution of Bachu paleo-uplift on the basis of former studies. Based on all of the work above-mentioned, this paper discussed tentatively about the relationship between oil accumulation and geological structure. The discuss involved how the structure controlled the reservoir characteristic and the effectivity of seal and trap. At last the exploration prospective area of Bachu paleo-uplift was pointed. By the synthesis analysis on tectonic evolution of Bachu paleo-uplift in Tarim basin, the results indicate that:(1)Six periods of fault structure activities was classified and the characteristic and machanism of them were given by each period;(2)The structural style, formation time and combination of relationship among the primary faults structure were established.(3)It is found that the decollement thrust structures developed in many areas of region, which took middle Cambrian gypsum series as their detachment surface.(4)Madong fold-thrust belt of Cambrian-Ordovician was not the foreland fold-thrust belt, the latter had some attributes of initiative but Madong fold-thrust belt exhibited some passivity and it was a associated structure of Tazhong strike-slip fault structure.(5)Structure controlling to oil accumulation was discussed: extensional faulting related sag of extention period controlled to the reservoir development; three-period karst were developed in the convergent time under the condition of uplift denudation; the type of trap and style of structure were controlled by the compressed strik-slip and seal detachment thrust foult; oil migration, accumulation and adjustment controlled by the different periods of paleo-uplift and pleo-slop falut; the fault uplift fixed in Holocene controlled to the location oil accumulated.