Optimization Research On High Temperature And Ultra-high Density Drilling Fluid In North Slope Area Of Central Tarim

The high temperature and high pressure deep oil and gas drilling project which carried out in the North Slope area of central tarim basin is faced with the worldwide technical problem which seriously restricts the exploration and development process of project in this area.How to regulate the high density water-based drilling fluid lon-term property stability under high temperature environment is the key to solve the promble.Therefore,it is urgent to study the mechanism and new method of high temperature stability regulation of high density water-based drilling fluid.Based on the analysis of high temperature and high density drilling fluid performance regulation difficulties,this paper researched the influence of high temperature on properties of clay minerals,main drilling fluid additives and weighting materials in the drilling fluid and clarify the difficulty of poly-sulfide drilling fluid performance regulation under high temperature environment.The regulation method of high temperature and high density water-based drilling fluid lon-term property stability under high temperature environment was put forward:using chemical deoxidizer inhibiting free reaction to improve the heat resistance performance of polymer agents;at the same time,using cross-linking inhibitor to slow the excessive cross-linking reaction of sulfonation treating agent under the action of high temperature for a long time,which is beneficial to improve the lon-term stability of drilling fluid under high temperature environment.The physical and chemical properties of different barite powder weighting agents were evaluated by means of XRD,SEM,particle size analysis,wetting angle and viscosity effect test,and their effect on the properties of high density drilling fluid were studied.The high density drilling fluid performance control method was proposed which based on the barite weighting material granularity reasonable distribution.The mechanism of this method is as follows:let weighting particle under the premise of fully dispersed,mixture two kind of particle which has grain size magnitude difference in certain proportion garding,can make the drilling fluid has the reasonable particle size distribution which is not only benefit to form multi-stage effective filling and achieve the dense packing effect to improve the quality of filter cake,but also play a smaller particles“bearing”and drag reduction to improve the rheological property,which eventually effectively improve the comprehensive performance of high temperature and high density drilling.Based on the dynamic change characteristics of the main properties of polysulfonated drilling fluid under the high temperature with long time(10-15d),a new comprehensive properties regulation method of high temperature and high density drilling fluid in the North Slope area of central tarim basin was proposed.On the basis of the main single agent optimization experiment,using high temperature crosslinking inhibitor to delay the excessive crosslinking reaction of sulfonated agents to the greatest extent under high temperature environment with long time,combining the weighting material particle size gradization optimization method and so on.Four sets of high density and high temperature drilling fluid formulations which are suitable for complex stratum condition and requirement of drilling technology in the North Slope area of central tarim were constructed.The density range of these formulations is 2.0-2.3g/cm~3,and temperature resistance is 180-200℃,the lon-term heat resistance is also outstanding of these formulations that keep the performace in a relatively stable state under high temperature environment with 10-15d.Meeting the strict requirement of lon-term high temperature stability of drilling fluid for the deep high temperature and high pressure oil and gas drilling and completion project in the North Slope area of central tarim basin and providing the technical support of drilling fluid for the deep high temperature and high pressure oil and gas drilling development in this area.