Study On Drilling Fluids For Protecting Reservoir Of Jilin Oil Field

Some problems exist in the drilling fluids used in Jilin oil field at present, the main of which is that the inhibitive properties of the drilling fluids are poor. This will damage the reservoir severely, which may influence the discovery of reservoir and give disadvantages to the exploration and development of oil field. In this paper, the drilling fluid is studied according to the on-site conditions of Jilin oil field.The reservoir sensitivities of the main formations of Jilin oil field is studied according to standard experiment process and the below results are got:The sensitivities of Well Fang 54 in Yingtai area from strong to weak are:Salt sensitivity(strong medium), water sensitivity(medium), alkali sensitivity(medium), velocity sensitivity(weak).The sensitivities of Well Yi 50 in Yitong area from strong to weak are:Water sensitivity(strong medium), salt sensitivity(medium), alkali sensitivity(medium), velocity sensitivity(weak).Considering of the long period and mass workload of the evaluation of sensitivities, the Artificial Neural Network is used in the evaluation process and corresponding software is programmed. The accuracy and reliability of the software can satisfy the need of on-site use.The measures on drilling fluid to protect the reservoir are set down according to the evaluation results of sensitivities:(1) change the kinds of ions in drilling fluid to be similar to the formation water and increase the salinity of drilling fluid over the critical salinity. (2) decrease the content of solid phase in drilling fluid, especially for the content of sub-micron particles. (3) adjust the size of solid particle according to the size of pore throat and select the rigid particle as the bridge particle. (4) use the flexible temporary blocking agent. (5) enhance the quality of mud cake, decrease the filter loss of drilling fluid, especially for the filter loss in high pressure and high temperature. (6) select the suitable treating agent to drilling fluid.A drilling fluid that can protect the reservoir, organic silicon drilling fluid, is developed. The result of experiment with this fluid shows that the permeability recovery value of core is high, which will benefit the discovery and protection of resevoir.