Papers by Keyword: Jiyuan Oilfield

Abstract: Jiyuan Oilfield Luo27 well field chang4+5 reservoir belongs to the typical three low" reservoir, which has tight reservoir, micro-fracture development and strong heterogeneity. After the water flooding development, there are many unusual phenomenons, such as profile absorbing water unevenly, injected water rushing in one direction seriously, block water cut rising rapidly, flooding wells increasing more. For that conventional dynamic adjustment and tracer monitoring are difficult to determine the inflow direction. In order to improve injected water utilization, Luo27 well field chang4+5 reservoir uses PI decision overall profile control technology to improve the injected water utilization, which effectively seals off the high permeability layer and eases the oilfield water cuts increasing speed and finally improves the water flooding recovery ratio.

Abstract: Discovered in recent years, Chang 4+5 reservoir group of Yanchang Formation in Jiyuan area is ultra-low permeability reservoir. The evaluation and prediction of the reservoir is the most critical technology in reservoir development. Comprehensive analysis with multiple research approaches shows that the storage potential of the ultra-low permeability reservoir is jointly controlled by sedimentation and diagenesis. Sedimentary factor includes lithology and sedimentary facies, two basic factors affecting the storage potential. The reservoir lithology is of fine-grained debris-arkose and miliary arkose. Pore types are mainly intergranular pores and dissolved pores. The sandstone microfacies in the delta front underwater distributary channel has the best storage potential. Diagenetic factors, including diagenesis types, evolution, intensity, combination etc., have direct influence on the reservoir storage potential. Compaction and calcite cementation are the main factors that weaken the storage potential, whereas carbonate dissolution, especially the dissolution of feldspar plays an important role in the improvement of the storage potential.

Abstract: Calcite cementation is one main cause for reduction of porosity and permeability. In the case of Chang 6 Member of Jiyuan Oilfield, calcareous interbeds have been investigated for the characteristics and genetic mechanisms within delta-front Chang 6 oil reservoirs so as to reveal their spatial distribution. As shown by research, carbonate content in this area more than 10% will significantly reduce reservoir porosity and permeability, as well as its oil-bearing property. In vertical, calcareous interbeds are commonly developed at interfaces, where mudstone contacts with either top or bottom of underwater distributary channels of delta front, or within channel sand bodies. Besides, underwater levees with intercalation of sandstone and mudstone and the delta-front channel bars at the top or bottom have found calcareous interbeds. Meanwhile, calcareous interbeds in plane mostly distribute in the under-Water distributary channels and also partly underwater levees. In research area, calcite cementation predominantly formed during late diagenesis, In the acidic water for under the action of carbonate cementation, provides Ca²⁺ 、Mg²⁺ and HCO_3- etc material base，Carbonate cementation content prong to accumulating at the top or bottom of neighboring mudstone and sandstone producing “calcite top” and “calcite bottom”.