Research Of Influence Factors And Methods On The Gas Quantitive Detection In Drilling Fluid For Reservoir

There are many factors to influence the reservoir's gas quantitive detection during drilling,which can be divided into geological factors and non-geological factors by a comprehensive analysis. Geological factors are the "signal" which the drilling fluid gas analysis wants to obtain, non-geological factors are the "noise" which needs to eliminate or reduce. This dissertation deeply studies and discusses the various factors and its elimination impacting the reservoir's gas quantitative detection during drilling on the basis of entirely analyzing drilling fluid gas detection's technological development and current status.First of all, study and discuss the affecting mechanism'of various impacting factors. Firstly,confirm the various geological factors of affecting the gas detection by analyzing the underground storage mode,phase transformation,chemical composition and composition parameters' character of different types of natural gas, as well as different types pore structure of fluid flow characteristics of reservoir. Through mathematical derivation to establish the calculating formula of the oil-gas amount in rock and the pores broken by bit and the oil-gas percolating and filtrating amount around the well bore formation. Secondly,research the influence of drilling parameters such as bit diameter and so on to the gas amount in drilling fluid by mathematical calculation; Analyze the variety regularity of reservoir's oil-gas percolating rate and filtrating amount with the variation of reservoir parameters, drilling parameters in lacking of balance drilling processes by using finite element simulation method; Find the relationship between drilling fluid viscosity and the trapping efficiency of hydrocarbon gas in the floating and electric trapper conditions by laboratory simulation. Thirdly, propose that the drilling fluid trapping and sampling position is more close to the wellhead, the analysis results are more able to reflect the true gas content in drilling fluid by analyzing; propose that drilling fluid volume processed by degassing device, degassing efficiency and the uncertainty of add air amount are the main reasons to impact the conventional electric degassing device can't quantitatively degassing; propose that gas processing unit "dead volume" will result in gas detection response lag, testing value distorted, as well as the equipment calibration results in unable quantitative detected TG and chromatographic analysis error.Then, research and discuss the revise method of various impact factors. To deduce the standardization values of the three drilling parameters,to make the gas detecting value in different drilling parameters normalized; To make the balance correction of gas logging data on the state of under-balanced drilling, eliminating the impact of under-balanced drilling condition; To deduce the mathematical relationship between the correction factor of various components and the viscosity and to correct the degassing efficiency in different modes of degassing; To quantitatively correct the value of TG by the relationship between the sum of chromatographic analysis and the corresponding values of TG in an chromatographic analysis cycle; The calibration curves are carried out by high-order polynomial regression, or piecewise polynomial regression to improve the accuracy of chromatographic analysis; Improve and develop the quantitative degassing and standardization gas processing system to reduce or eliminate the effect of degassing position, degassing devices and gas processing unit "dead volume".