Study On Formation Damage Mechanism Of JiLin Oilfield

Though the basic causes of formation damage are known, given a reservoir, we must analyze the idiographic reasons of it due to the variety of geology and formation condition. In this paper, basic data such as clay mineral content and pore texture of Jilin oilfield are analyzed according to standard experimental procedures. On the basis of it, systemic analysis of reservoir sensitivity of the main sections of Jilin oilfield is carried out, the result is as following: The reservoir sensitivities of Ying Tai section(represented by Well Fang 54) are: Salt sensitivity(strong medium), water sensitivity(medium), alkali sensitivity(medium), velocity sensitivity(weak); The reservoir sensitivities of Yi Tong section(represented by Well Yi 50) are: Water sensitivity(strong medium), salt sensitivity(medium), alkali sensitivity(medium), velocity sensitivity(weak); The reservoir sensitivities of Da Qingzi Well section are: Water sensitivity(medium), salt sensitivity(weak medium), alkali sensitivity(weak medium), velocity sensitivity(weak). Based on sensitivity analysis, a systematic study on formation damage mechanism is carried out, which indicates that the main reason causing formation damage is allochthonous fluids invasion resulting in drastic reduction of permeability. It's proved that temporary plugging technique is an effective method of preventing allochthonous fluid from invasion. On the basis of traditional "2/3"bridging law, this paper sets up fractal theory to optimal selection of temporary plugging agent and the current drilling fluid system of Jilin oilfield is also modified and improved. A series of experiments indicate that it has obvious effects on the reservoir protection.