Research On Reservoir Micro-property Gas Drive Mechanism Of Chang Bed In Wangyao Block Of Ansai Oilfield

Ansai Oilfield is located in the southeast part of Ordos Basin and the research area Wangyao Block is in the eastern part of the site. The study block develops delta facies controlled by river with provenance from northeast. Accumulation is located in the delta front with microfacies like underwater distributary channel, mouth bar and bay mud between distributary channels. The reservoir develops low permeability, low porosity and severe heterogeneity because of strong compaction and fine grains. At the same time, it is also filled with micro fracture and dissolved hole. Aimed at enhancing recovery factor, this dissertation has conducted several experiments to delineate the reservoir.Firstly, the scanning electron microscope was employed to define the type of pore and throat. Secondly, the pore and throat distribution and their relationship to reservoir property were ascertained through high pressure mercury injection test. Last, nuclear magnetic resonance test was conducted to find out the mobile fluid distribution and their link to reservoir property. All these experiments enable the reservoir to be recognized from micro aspects. And In order to understand it from macro aspect, two more researches are conducted. Firstly, the most fitting blowing agent for the field was picked from8different agents. Secondly, four kind of displacing experiment (water drive/nitrogen drive/nitrogen foam drive/water-gas alternating drive) were made to find the best stimulation method for Ansai Oilfield.Researches show that Chang6reservoir in Wangyao block of Ansai oilfield yields low porosity with low and even ultra-low permeability. The pore types include large amount of inter-granular pore and dissolved pore with feldspar and zeolite and minute inter-crystal pore. Meanwhile, reservoir develops micro throats which assume some typical shapes like schistose and curve. Core test denotes two peaks in T2indicating that with an average of31.27%,14.76-49.31%fluid is movable. In addition, Kongzhou zhongye ZYGP proved to be the best foaming agent for the block. Coreflooding experiments show comparing with other recovery methods, nitrogen foam flooding yielded highest displacement efficiency, so it is the most favorable recovery method for the reservoir.