Researches On The Damage Mechanism Of Low Permeability Reservoir In Langdong Oilfield

The oil reservoirs in Langdong Oilfield is typical low permeability sandstone reservoir. In recent years, Low permeability oil reserves in the geological reserve ratio increases obviously in China, it is very important for Chinese petroleum industry in the continuous and steady development to research it. Through the studies and analysis on the petrology and fluid properties of the reservoir, the experimental test of formation sensitivity, the experimental evaluation of completion drilling fluid and the experimental method that is established by the thesis for degree of damage, the following knowledge and achievements have been primarily obtained:(1)Packsand and medium-grained sand is the the main rock types, it consists of feldspar and quartz. Types of relict intergranular and intergranular emposieu in the main;Types of pointlike and lamellar throat in the main. The reservoir physical properties is poor as a whole, belong to typical in-low porosity and low-low permeability reservoir.(2)The content of main reservoir clay minerals for kaolinite, andreattite layer, is generally about 30%-40%, it also includes carbonate distributes on the surface of rock particles. They are the major sensitized material. Clay mineral normally adheres to the surface and fills pores, it is one of the main factors.of damage formation.(3) There is a strong water sensitivity, extremely-strength salt sensitivity, the middle-strong alkali sensitivity and velocity sensitivity and weak stress sensitivity damage. Acid sensitivity has close relationship with the permeability of the reservoirs..(4)The grey interrelation theory can forecast the sensitive degree of damage, it is an ideal method for simple and reliable.(5) The type of temporary shielding plugging drilling fluid system meets the reservoir completion drilling fluid in conventional performance requirements. Experimental results have shown that a shielding temporary plugging agent of drilling fluid system can better protect reservoir.The results of this paper is the foundation for the understanding of the mechanism of formation damage and protection of the low permeability reservoir in Langdong Oilfield, at the same time, also on the mechanism of formation damage of the similar low permeability reservoirs has important guiding significance.