Study On The Impact Of Reservoir Heterogeneity On Hydrocarbon Accumulation And Distribution

The exploratory practice reveals that: although some large-scale oilfields have been found in recent years, the exploratory targets of many old oilfields have already turned from simple large-scale hydrocarbon reservoirs to multiple complex small-scale ones. Under such situation, lithologic hydrocarbon reservoirs become the main exploratory target of many oilfields, but due to the random and disperse distribution, middle or small scale, and strong reservoir heterogeneity of sand bodies of these lithologic hydrocarbon reservoirs, the understanding of hydrocarbon accumulation and distribution in lithologic traps is still not very clear, which restricts the development of petroleum exploration. In addition, researches on the impacts of reservoir heterogeneity on petroleum accumulation and distribution are still not enough, in spite of many researches on oil and gas accumulation theories, exploratory reservoirs, and the relations between reservoir heterogeneity and petroleum exploitation.This thesis took Niuzhuang low-lying as the study area which was typified with abundant lithologic hydrocarbon reservoirs in the middle part of the third member, Shahejie group (Es32). Combined various field and laboratory data with physical modeling experiments of hydrocarbon accumulation, the impact of reservoir heterogeneity on hydrocarbon accumulation and distribution were studied, and the conclusions were as follows: (1) The puzzles whether turbidite sand bodies contained oil or not, how oil concentrated heterogeneously in the low-lying, and why the oil contents varied greatly in different sand bodies were ascribed to source rock, faults and sand bodies in the strata of Es32. (2) The impact of reservoir heterogeneity on hydrocarbon accumulation and distribution were analyzed systemically, and the results included:â‘ In plane, the distribution of petroleum were controlled by the sedimentary facies, in which the relatively homogeneous turbidite channel was the most favorable facies for hydrocarbon accumulation; the more irregular the sand body was, the more difficult it was filled up by oil; the center of sand body had good hydrocarbon enrichment than the margin; oil production in the early days that stood for primary petroleum distribution in the reservoir had positive correlations with the"induction number"which reflected the heterogeneous degree of sand bodies.â‘¡In vertical, as for interlayer scale, oil saturation had no positive correlations with the porosity and permeability, while had some relations with the burial depth under the effect of petroleum accumulation environment. As for the intra-layer scale, rhythmicity of oil saturation was accordant with which of the porosity and permeability; within all the beddings, the homogenous massive one was most favorable to petroleum accumulation; thick sandstone type in the sand-shale assemblage was good; and the interbed served as barrier for fluid flow, it may result in several oil/water contacts and may lead to unsaturation of petroleum in the reservoir.â‘¢In microscopic scale, both primary pores and secondary pores served as the reservoir space of the Es32 strata in Niuzhuang low-lying, and there were three types of pore configuration, in which type I with middle-pore-middle-throat was the main storage space; Under the impact of diagenesis heterogeneity, petroleum distributed mainly in the turbidite channel facies and the nearby sandstones of the boundary faults around the low-lying, especially the downthrown block with abnormal high pressure. (3) On the basis of the above researches, the theory"reservoir heterogeneity controlling hydrocarbon"was preliminarily founded. Combined with example analysis, its broad applicability was stated, and the theoretical and practical values were pointed out. In theory, it was a potent supplement for the traditional hydrocarbon theory and a result that the hydrocarbon accumulation theory developed to multiple and fine field. In practice, it played an active role on the exploratory orientation evaluation, reserves calculation, well deployment, water injection and so on.