The Low-Permeability Reservoir Chracterizations And Its Exploitation Effect In Erdos Basin

Chang 6 member reservoir in GanGuYi oilfield is at a high degree of exploitation. Because of the reservoir pore structure and the effects of heterogeneity, the oil exploitation become more and more difficult. Based on petrology, well logging sedimentology, reservoir assessment, geological modeling and petrophysics experiment analysis technology, Chang 6 member reservoir have been researched including sedimentary characteristics and pore structure characteristics, the percolation mechanism and the influence on water flooding development, which can provide the basis for further development in the study area late.Based on the spot with the special markers, Chang6 reservoir member can be subdivided into four submembers, long 6 section of the reservoir in yanan delta sedimentary environment with advancing basin lobate or digitate characteristics, and can be separated by a bay, in the delta front subfacies. On the basis of logging response characteristics and the lithology analysis, the sedimentary facies can be divided into underwater distributary channel, distributary bay and river channel lateral margin. The types of the reservoir diagenesis of Chang 6 member mainly includes compaction, pressolution, cementation filling the role and dissolution. The reservoir diagenesis is at the stage of A2-B period of late diagenesis. Main experience of diagenesis are:(1) the precocious early stage of rock mechanical compaction and clay membrane separation;(2) at late stage of quartz, feldspar, pressolution and secondary pores increase;(3) the late diagenetic stage of early diagenetic authigenic mineral precipitation and its caused by cementation filling and subsequent, debris, mica and feldspar calcite dissolution, such as formation of secondary pores.Due to the strong diagenesis, dissolution, it makes Chang 6 reservoir changed into low porosity, low permeability of tight sandstone reservoir.(4) the late diagenesis, in the middle of the feldspar dissolution, and clay mineral and laumonite dissolution occurred in cement, with the increasing of the dissolution, produce secondary pore, is a complement to the primary pore. Dissolution of chang 6 reservoir sandstone reservoir is relatively less strong compaction and cementation, formed by dissolution pore proportion in the total porosity. And formed by compaction and cementation residual intergranular pore is the district 6 primary pore reservoir, its proportion in the total porosity of 41.5% on average. Diagenesis make chang6 reservoir primary pore loss is serious, the dissolution of late diagenetic a lot of secondary pore, makes the porosity and permeability of sandstone have been recovery.Chang 6 member is characterized by the period of storage layer upon layer and interlayer heterogeneity, strong interlayer is given priority to with mudstone interlayer, containing silty mudstone, tuff and so on other types of isolation layer, single sand body of interlayer heterogeneity between sand have strong with the weak performance, and Chang 61 and Chang 62 are characterized by strong heterogeneity, on the other hand, in Chang 6 member, the distributary channel sand body sandwich frequency is relatively high, reflecting the points of the strong heterogeneity, produce certain effect on production and development. The influence of each small layer internal permeability change of single sand body is more complex, with positive rhythm, the rhythm and composed of positive and reverse rhythm superposition compound rhythm type three types, type law is to be the most common. Chang 6 section of the reservoir is divided into three kinds of pore structure, the parameters of different pore structure differences, different pore types and the seepage characteristics of diagenetic facies of reservoir. From reservoir diagenetic facies study, feldspar and laumonite dissolution of secondary pore dissolution facies, good pore structure, seepage capability is strong, and secondary porosity is relatively not development, part of the interval of the residual intergranular pore larger area, development ? type of pore structure, reservoir seepage ability of medium, and for residual intergranular pore, mainly chlorite cementation dissolution facies and carbonate cementation facies, pore structure is poorer, give priority to with ? type of pore structure, seepage ability is low, recovery efficiency is low. In Tang 114 and Tang area, Chang 6 reservoir is influenced by pore structure and reservoir property, different after water injection well group development, and production capacity in the late effect difference is bigger.