The Beach-bar Sand Body Causes And Development Of Low-permeability Reservoir Countermeasures

Dongying sag is in the jiyang depression of bohai bay basin. After50years ofprospecting and developing,33oilfields have been found, and the proven reserves is2.488billion tons. It has become a very important oilfield. Beach-bar sand body ismain sedimentary reservoir of the upper part of the fourth member of the Shahejieformation (Es4s) in the west part of Dongying depression, and the reported provenreserves of beach-bar sand body is0.14billion tons. Because of the strongheterogeneity of the Es4member reservoir and the complexity of oil distribution，thecost of exploration is very high, which constrained the efficient development of thisarea. Thus exploring the formation distribution rules of beach-bay sand body,precisely predicting the reservoir distribution, understanding the penetratingmechanism and building the effective developments becomes the master keys torealize efficient development of beach-bay sand body.Combined with some previous results, analysis of various material basics, Isummarized the geological characteristics, fluid property and formation energycharacteristics of the low permeability beach-bar sand body in dongying sag in thispaper. Through the combination of laboratory test and field test of pilot area, Idiscoveried series of suitable technology and development for low permeabilityreservoir characterized beach and bar, and evaluated the adaptability of thesedevelopments. I also did some work in improving reservoir reserve producing rate andrecovery, which made some significant progress. I achieved some new understandingin the aspects formation distribution rules, microscope characteristics and developingtechnologies, which are verified in field practise.The main achievements are as follows:(1) Cleared the controlling factors and distribution laws of beach bar sandstone,built the deposition mode of the foreshore-shallow lake bar sand body. The ancienttopography and wave base control the range of beach and bar sands development, theancient hydrodynamic controls the beach bar sand facies differentiation, datum levelchange controls beach bar sandbody superposition style. Subdivided beach bar phase as the dam sub-phase and beach sub-phase, among which dam sub-phase can bedivided into microfacies of the main dam and the margin of dam, and beach sub-phasecan be divided into microfacies of beach creast and beach matS.(2) Built the geological prediction method and the thin reservoir earthquakedescription technique based on sand control mechanisms of the beach and bar sandsreservoir. Used high-resolution sequence stratigraphic analysis to determine thebeneficial layers of beach and bar sands, used sedimentary facies, ancient landformsand ancient hydrodynamic analysis to determine the favorable distribution of beachbar sandstones. I also used integrated geophysical techniques to determine the beachbar sandstones exploration targets.(3) Built percolation theory and development technology basing on the beach andbar sands reservoir. Considering the thick dam sand reservoir and relatively goodproperties, this paper built the developing technologies as small well spacingwaterflooding, vertical well injection together with horizontal well production; Andfor the reservoir with poor property and multiple layers, large scale fracturing shouldbe done; For the reservoir with stable distribution and poor water absorption capacity,CO2miscible flooding procedure should been taken.