Study On Drilling Overflow Monitoring Method And Application For Pressure-Sensitive Formation

In recent years,China's oil exploration and development have been moving toward the deep and complex formation.In Sichuan and the Tarim Basin,this problem of formation's pressure sensitivity is universal because there are often complicated downhole conditions such as the malignant loss formation,the high-pressure formation,and the narrow-density window formation in the process of drilling.Frequent overflow and loss problems during drilling lead to one of the main reasons of safety accidents and low construction efficiency in the type of formation.At this stage,the methods of monitor overflow include mainly flow-out method,mud pool level method and standpipe pressure method by monitoring the ground parameters.And the new technologies of overflow monitoring such as PWD and downhole micro flow monitoring have also been introduced.Although the ground parameter monitoring method is economical,it lacks the grasp of the downhole conditions,and there is a certain degree of delay.Although the downhole monitoring method is timely,there is also a shortage of poor stability and high cost.In view of this,this paper carry out the study on drilling overflow monitoring method for pressure-sensitive fonnation.Based on the drilling overflow characteristics of pressure-sensitive formation and combined with the advantages of the flow-out method that can provide early overflow or well leak indication most quickly and accurately,this article selected the flow-out method as drilling overflow monitoring method for pressure-sensitive formations.In view of the disadvantages of the flow-out method on the inaccurate monitoring of export flow and the lack of understanding in the downhole pressure conditions,this paper put forward using a combination of surface flow monitoring and downhole pressure analysis to monitor and predicting drilling overflow of pressure-sensitive formation,and established a set of the drilling overflow monitoring program for the pressure-sensitive formation.In order to solve the problem that the conventional flow-out method can not accurately monitor overflow in the process of pull out of hole and run in hole,this paper,based on the conservation of flow and the working condition of string,established the correcting model of the export flow and the calculation model of the downhole vacuum volume for the tripping process,and proposed the over-flow judgment method for the flow-out difference;In order to enhance the mastery of the downhole pressure condition,this paper analyzed the relationship between bottomhole pressure and overflow,and established a steady and transient calculation model of surge pressure.Then,this paper developed a program to calculate surge pressure,that was used to analyze the effects of parameters on the downhole surge pressure such as the working conditions of string,the operating speed of string,the displacement of pump,and the rheological properties of drilling fluid,and studied the the relationship between the downhole surge pressure and overflow,and the influence of the downhole surge pressure for controling overflow.Finally,based on the actual conditions of the drilling site,combined with the overflow characteristics of the the pressure-sensitive formation,this paper analyzed the hardware and software requirements of the drilling overflow monitoring and simulation system,and carry out the overall design for the system.At the same time,this paper studied the signal detection instrument for flow,density,pressure,drilling fluid and bit position,optimized the signal detection instrument suitable for this system.And this paper designed the scheme of data acquisition and data transmission based on the SCW-530 logging wireless sensor acquisition system,optimized the data acquisition and data transmission instrument suitable for this system.Based on the research of the above theoretical methods,calculation models and equipment,this paper,Visual Studio 2015 and Sql Server 2008 as the platform of development,use C#develop the software of drilling overflow monitoring and simulation,which integrates computer data collection,surge pressure analysis and overflow monitoring.And applied the software in the field,The application results show that the established the drilling overflow monitoring program for the pressure-sensitive formation can improve the conventional flow-out method in the problems that can not accurately monitor overflow and the lack grasp of the downhole pressure condition in the process of pull out of hole and run in hole,have important significance for ensuring drilling safety.