Researches Of Gas Extraction During Screening Of Drilling Fluid In Shale Shaker Of Closed Circulation System

In the process of underbalanced drilling,because the pressure of the drilling fluid is less than the formation pressure,the formation fluid will enter the wellbore and return to the surface,causing damage to the equipment,drilling site personnel and the environment,so the drilling fluid needs to be treated.Conventional underbalanced drilling is applied to the formation without harmful substances such as hydrogen sulfide,so the drilling fluid returned from the well can be separated by conventional surface separation system;if the formation contains hydrogen sulfide or volatile hydrocarbons,the drilling fluid must be used Closed circulation drilling system performs cyclic separation.Because the closed system can separate the drilling fluid under closed conditions,and the separated waste and hazardous materials are properly treated,it is a necessary equipment for underbalanced drilling operations in sulfur-containing formations.China has not fully mastered the core technology of closed-cycle drilling and the lack of key equipment such as four-phase separators.Coupled with foreign technology monopoly,it has seriously hindered the process of solving the technical problems of drilling high-sulfur pressure-sensitive reservoirs.Therefore,a closed circulation system with a liquid-gas separator and a closed shale shaker as the core equipment has been proposed.Aiming at the problem of gas escaping during the vibratory screening of drilling fluid in a closed circulation system with a liquid-gas separator and a closed shale shaker as the core equipment,this paper proposes a gas-extraction scheme for a closed shale shaker.The hydrogen sulfide gas is mainly used as a research object.The amount of hydrogen sulfide gas released during the process,the effects of temperature and pressure in the shaker and the vibration of the shaker on the gas-liquid separation of drilling fluid were analyzed;in order to achieve high-efficiency extraction of hydrogen sulfide,a closed shaker gas extraction system was optimized Scheme;Theoretical analysis and numerical simulation methods were used to analyze the effect of the extraction pressure of the closed shale shaker extraction system on the processing capacity of the drilling fluid shale shaker.The research on gas extraction in the closed shale shaker is helpful to break the blockade and monopoly of foreign closed cycle technology and form a practical technology with distinctive characteristics.It provides a feasible technical means for solving the problem of underbalanced drilling in sulfur-bearing formations.The main work of this article is as follows:(1)The amount of hydrogen sulfide gas precipitation at different internal pressures of the liquid-gas separator and the internal pressure of the shale shaker is Calculated,and the effects of the temperature of the drilling fluid and the pressure in the shale shaker on gas-liquid separation is calculated and analyzed using MATLAB.The simulation method simulates the influence of the vibration characteristics of the shale shaker on the gas-liquid separation process,and studies the law of gas precipitation from the drilling fluid during the shale shaker working.(2)Fluent is used to perform the numerical simulation of the hydrogen sulfide gas extraction process in the vibrating screen,and the design-expert is used to design the vibrating screen gas extraction numerical simulation test plan.According to the results of numerical simulation of the hydrogen sulfide extraction efficiency of each group of experiments,a response surface model of gas extraction efficiency in the vibrating screen was established.Combined with the single-objective optimization method,the optimization calculation and analysis of the model are carried out,and finally the extraction system scheme with the best extraction efficiency is obtained.(3)According to the basic principle of fluid mechanics,the motion equation and continuity equation of drilling fluid flowing on the screen and passing through the screen under negative pressure in the shale shaker are established.The flow field simulation of the shale shaker under negative pressure above the screen was established using Fluent,and the drilling fluid flow theory and numerical simulation results of the drilling fluid vibrating screen under gas extraction were compared to verify the accuracy of the numerical simulation method.The numerical simulation method was used to analyze the effect of the shale shaker gas extraction scheme of the closed circulation system on the drilling fluid treatment capacity,and the feasibility of the extraction system was verified.