Research On Formation Protection Technique In Yingtai Area Of Jilin Oilfield

Though the basic reasons of formation damage have been profoundly understood, due to differences in geological characteristic and formation condition and so on, detailed analysis of each oilfield should be carried out. There are a lot of technical problems in drilling fluid of Jilin oilfield, the remarkable one is that low-inhibiting drilling fluid damages formation to a large degree and is harm to formation discovering and protection and influences development rate and effects of oilfield. Therefor, how to advance the inhibition of drilling fluid and induce liquid and solid contents that invade into formation becomes the chief problem of formation protection in Jilin oilfield. According to standard test procedure, research on formation sensitivities of Yingtai area have been conducted, the results are as follows: Salt sensitivity (medium to high), water sensitivity (medium), alkali sensitivity (medium), rate sensitivity (low). Considering the time taken in sensitivity evaluation and large workload and so on, artificial neural network has been introduced into sensitivity evaluation, evaluation model has been instructed and computer software has been compiled. The accuracy and credibility of the model has been proved. On the basis of sensitivity analysis, research onformation damage mechanism of Jilin oilfield has been conducted, damage simulating test proves that the main reason causing formation damage is invasion of exotic fluid into formation.Temporal plugging technique is one of the effective methods to prevent invasion of exotic fluid, in the paper, fractal theory has been adopted in optimal selection of temporary plugging agent. A lot of experiment researches have been conducted to indicate that temporary plugging fractal theory has obvious application effect. On the basis of original drilling fluid of Jiling oilfield, formation protection drilling fluid-organic silicon drilling fluid has been developed, a lot of tests indicate that the system has high permeability recovery which is in favor of formation discovering and protection.