Investigaiton Of Drilling Fluid System And It's Application In Yuedong Oilfield

With the development of ocean exploitation,offshore oil and gas industry has sprung up,the average annual growth rate reached 32.3%,which has been the pillar industries of marine economy in China.In addition,the onshore oil fields have gradually entered the development stage of high water cut,extra high water cut and reduced output,and the oil fields in eastern China generally paid their attention to the areas with shallow water depth of less than 10 meters.Experts believe that this area has become the important aera for oil exploration.Due to the increasing demand for oil and other non-renewable resources,the offshore oil exploration was important.Hainan—yuedong oilfield is a shallow sea area,The complex geological characteristics of the dongdong oilfield was investigated.KCl-Sepolycol drilling fluid system was developed.At 70 oC,the mud loss could be controlled in 7 mL.For inhibitive evaluation,the shale recovery rate was as high as 97.3% and the invasion depth in formation was 3.1 cm,the recovery of permeability was 93%,significantly better than the other drilling fluid system.It was suitable for the applications in shallow sea area.Non-Solids SPK drilling fluid system was also investigated,which resolved the shortcoming of large water loss with non-solid drilling fluid.At 70 oC,the water loss was controlled with 8.4 mL.The addition of 0.1% fungicide had little side effects on drilling fluid system performance,fortunately,it was used to improve the corrosion resistance of drilling fluid.For both of the systems,the anti-lithology rate of reached 10% and the cement pollution rate was 1.5%.The optimal amount of gel breaker was 5% in the protection fluid for RP reservoir,and the gel breaking rate was more than 57%.The various measures of the protection fluid for RP reservoir remained the same even staying understand at 63-64 oC for 7 days.After 15 days of soaking,the mud shale has not been hydrated,which indicated the inhibition be completely satisfied with the construction requirements.Based on the site operation combined with the desk research,the large bring cuttings and anti-sticking,the enlargement of hole diameter in mud stone,density control and reservoir protection were all resolved.The satisfactory result was obtained in field application and the considerable economic benefits were achieved.