Research And Application Of High Temperature Drilling Fluid Technology For Well Songke-2

Scientific drilling provides Earth science with unprecedented observational data and the opportunity to verify key hypotheses,and is the most direct and effective way for human beings to obtain information from the Earth's interior.Ultra-high temperature drilling fluid has been playing an irreplaceable role in ensuring safe and efficient operation of the ultra-deep well scientific drilling wells.The main components of water-based drilling fluid,such as water,clay,all kinds of functional treatment agents,etc.showing certain temperature sensitivity,are responsible for the difficulty of high temperature drilling fluid preparation,performance change mechanism analysis and performance control.Especially for drilling fluid high temperature rheology,which is directly related to the drilling operation of many aspects,like cuttings suspension and carrying,flowing pressure drop,rock-breaking efficiency and etc.Hence,it is of great engineering and scientific significance to determine and analyze the characteristics of drilling fluid rheology in high temperature environment.First of all,this paper summarizes the mud system used in scientific drill drilling at home and abroad in recent years,and clarifies the key points of the selection and performance control of the drilling fluid system in different sections.Results show that,in the view of the need of geoscience research,requirements for high core quality,high core recovery rate of science drilling,lack of geological data in construction areas,high risk encountered in drilling complex formations,they cause great difficulties to coring process selection,well structure design and so on.Drilling fluid design and its performance regulation need to meet the requirements of long-term stability of the borehole,adaptability to a variety of coring processes,and help in the performance of down-hole power tools.Secondly,the paper introduces the basic information of the Songke Well 2,including well location selection,stratigraphic conditions,well structure,etc.According to the related drilling design and geological design,the design point of drilling fluid for different formation and every spudding,which is divided into the water sensitivity of the upper stratum,the high temperature anti-collapse resistance of the three spudding,and the ultra-high temperature problem below the fourth spudding,was ensured.Then,the important test instruments and methods,such as high temperature and high pressure(HTHP)rheometer,roller oven,high-temperature high-pressure filtration device are presented.At the same time,the basic principle of the least square method and the feasibility of high temperature rheology fitting for drilling fluid are described.Again,the aging test and HTHP rheological test are carried out on the influence of high temperature on the commonly mud-making clay(bentonite,attapulgite and sepiolite).The effects of clay types and additions,salinity,test temperature and other factors on their high temperature rheological properties are elaborated.The results show that at 8% addition,the viscosity of the bentonite slurry increased first and then decreased with increasing temperature.The sepiolite slurry exhibits similar characteristics,but it is not as obvious as the bentonite slurry,and the viscosity of the attapulgite clay decreases continuously with increasing temperature.When the temperature increases from 40°C to 220°C,the apparent viscosity retention rates of the three are as follows: in the presence of inorganic salts,the viscosity of the bentonite slurry significantly reduces,and the viscosity stability of the attapulgite and sepiolite slurry is enhanced.Note that the rheology of the aged attapulgite and sepiolite slurry is extremely abnormal and cannot be fitted by conventional rheological models.The fourth chapter focuses on testing the factors affecting the rheological properties of macromolecular polymers solution,including polymer types and its dosage,salt,shear time,shear rate,p H value,and oxygen scavenger.The results show that the viscosity of the most macromolecular is basically lost at high temperature;The more the salt dosage,the higher the shear rate,the longer the shear time,the higher the p H value,the larger the attenuation range of the viscosity is;the presence of oxygen scavengers and formate has a good effect in stabilizing the viscosity of the polymer solution.Further,the simple polymer solution is suitable to be characterized by a power-law model,when the temperature rises,the consistency coefficient decreases and the flow index increases.Mixing it with mud-making clay can greatly increase the viscosity stability of the system.Moreover,aging tests demonstrate that common high temperature treatment chemicals,such as sulfonated materials,SPNH and SMC,as well as a variety of high temperature polymer,will suffer a certain high temperature reduction,especially in the presence of inorganic salts.However,compared with the inorganic salt,the addition of formate alleviates the performance degradation of various treatment chemicals.The fifth chapter,on the basis of the previous results,develops the drilling fluid formula resistant to 245? and evaluates its comprehensive performance.The evaluation results show that the system has outstanding comprehensive performance,including exceptional thermal stability,good rheological and filtration properties,strong inhibition,excellent lubrication and strong anti-pollution ability,and is in the process of turbine core drilling at the drilling site.Another developed high temperature and solid-free brine drilling fluid formula perfectly solves the problem of barite blocking in high speed centrifugal coring in the turbo drilling site.The sixth chapter expounds the drilling fluid usage and performance control ideas and methods of every spudding during the implementation of the Songke Well-2,and summarizes and reflects its advantages and disadvantages.In general,on the basis of clarifying the influence of high temperature on the components of drilling fluid,this study takes full account of the performance requirements of every spudding,as well as the convenience of the conversion of drilling fluid system,the continuity of performance adjustment and the economic cost of the overall use of drilling fluid.It is recognized that only by means of a variety of testing methods to find out the influence of high temperature on the performance of drilling fluid components,it is possible to guide the preparation and performance regulation of high temperature drilling fluid.On the completion of indoors research,this paper has carried out engineering verification,enriched the knowledge of high temperature drilling fluids,thus providing reference for the progress of high temperature drilling fluids technology in ultra-deep oil and gas wells and hot dry rocks.