Research And Application Of Plugging And Collapse Prevention Technology Of Horizontal Section Shale Drilling Fluid

Unconventional exploration and development of oil and gas resources has become the focus of China’s energy development.The geological conditions of this oil and gas reservoirs are complicated.In order to increase the drainage area of the oil and gas,the horizontal wells with long horizontal section are constructed.Unconventional oil and gas reservoirs and horizontal sections are mainly shale.This rock is high clay mineral content,poor cementation,stratigraphic micro-cracks and bedding development.The water or drilling fluid filtrate into the micro-cracks easily,which destroy its original balance,resulting in rock off and off the block.Based on the above problems,this paper mainly focuses on the research of plugging and collapse prevention technology of horizontal section shale drilling fluid.By studying the research progress of anti-collapse agent and the shortcomings of the existing anti-collapse agent of mudstone drilling in the unconventional well,a high efficiency anti-collapse agent CAG was developed.The sludge asphalt material was the raw material of the agent,and it was prepared by the technology of surface hydrophilicity modification.The CAG agent had good plugging and anti-collapse performance,and superior to the common asphalt product.Pilot production showed that: the production formula was feasible,the production process was reasonable;and the indicators of product performance were able to meet the requirements.The anti-collapse mechanisms of the CAG were as follows: adaptive plugging feature,"membrane+skeleton" structure,and multple synergie effect.In order to develop anti-collapse drilling fluid system,the main treatment agents(flow regulatorf,inhibitors,coated flocculant,filtrate reducer,lubricants)in the anti-collapse drilling fluid system were optimized.Then the anti-collapse drilling fluid system for shale formation was developd,and its main performances were evaluated.The preferred coated coated flocculant and inhibitor can inhibit the shale hydration dispersion,and the selected lubricant can meet the needs of the horizontal section drilling.The plugging and anti-collapseperformance of the drilling fluid system was very sterong,close to the characteristics of oil-based drilling fluid.The sysytem had strong ability to carry cuttings,can meet the needs of the horizontal section of shale drilling.The plugging and collapse prevention technology of horizontal section shale drilling fluid was successful applicated in the 2 blocks of 2 wells in Changqing oil field.The Field tests show that the drilling fluid system can stabilize the wellbore wall,and there was no underground complex situation happened.It effectively solve eroded,lost blocks and other serious well instability in horizontal section drilling mud shale formation,which ensure the normal drilling process,and reduced the production cycle greatly.