Research On Wellbore Thermal Effect Of Deepwater Drilling

Nowadays,the oil reserves of the land gradually decrease.Deepwater oil and gas exploration has become the focus of current research.Deepwater drilling is a very important part of deepwater oil and gas resources development.With the increasing of water depth,the operation difficulty of deepwater drilling is also increasing.One of the key factors that affects deepwater drilling is temperature.In deep water drilling,the change of the temperature field of the wellbore is complex,so it is very important to predict the wellbore temperature field in the deep water environment to prevent the downhole accidents.In this paper,the unsteady heat transfer model of the well bore in deep water drilling is established through the law of conservation of energy,the theory of heat transfer and the related characteristics of deep water,and the model is discrete by the method of full implicit difference.Finally,the sensitivity analysis of the phase parameters affecting the temperature field is analyzed with Gauss Seidel iterative solution,and the program for calculating the temperature field of the well bore in deep water drilling is developed by using MATLAB.Secondly,in order to prevent the collapse and rupture of the well wall in the process of deep water drilling,it is necessary to predict the wall collapse pressure and fracture pressure.In the past,the research on the stability of the wellbore has not taken into account the effect of thermal stress on the wellbore,and the effect of thermal stress can not be ignored.Therefore,it is necessary to calculate the wellbore and formation temperature by establishing the well wall and the formation temperature field,and then combine the thermal elastoplastic theory to calculate the circumferential stress under different cycle time.In view of the effect of the additional thermal stress on the collapse pressure and fracture pressure,the safety density window of the drilling fluid is obtained.Finally,through the rock mechanics experiment of rock strength affected by temperature,the influence of temperature difference on drillability and drilling speed is changed by temperature variation measurement,and the influence of temperature on rock strength is determined macroscopically,and the relationship between temperature difference and modulus of elasticity and Poisson's ratio is established by using the empirical formula to calculate the time difference of sound wave,thus the temperature is determined theoretically.The influence of the change on the formation parameters.The influence of temperature changes on the formation parameters is taken into consideration in the study of the stability of the wellbore,and the accurate safety density window of the drilling fluid is obtained,which provides guidance for the field operation.