Logging Response Characteristics And Evaluation Methodology Of Drilling-fluid Invaded Formation Damage In The Dongfang 13th Block

The logging response characteristics and evaluation methods of reservoir formation damage are actually a logging evaluation method in drilling fluid invasion time dimension.According to the different logging response characteristics before and after formation damage,and the depth of mud invasion,the changes of formation porosity,permeability and saturation,a high-precise logging solution for the evaluation of raw formation and damage degree after invasion is established,it can change the present overreliance on experience in the formation damage evaluation.This paper brings out research based on the background of reservoir formation damage caused by high density mud invasion in the Dongfang 13 block,based on the reservoir formation invasion damages mechanism,laboratory experiments of formation damage degree and the previous advanced method of reservoir parameter evaluation using logging,a series of cores logging response experiments before and after mud invasion are carried out,the two main logging difference response characteristics of fluid replacement and the change of reservoir pore structure occurred after the drilling fluid invasion have been captured by experimental data analysis,Through deep analysis of invasion depth,the correction ofresistivity after drilling fluid invasion,the evaluation method of logging interpretation permeability based on pore structure representation,the damage correction of NMR T2 spectra,and so on,the raw and damaged formation logging evaluation technology has made a great breakthrough and achieved the high-accuracy invasion evaluation,which provides a good example for the logging method interdisciplinary application of the geology and drilling engineering.The main results achieved and understanding are as follows:Firstly,On the basis of in-depth analysis of the abundant experimental data of T2spectrum of NMR,resistivity,sonic and capillary pressure measured by simulating the process of drilling fluid invade into the core samples,a three-segment model of drilling fluid filtration loss and invasion depth under the condition of classification of permeability has been established,the sensitive order and difference response of logging data of drilling fluid invasion is obtained,and a new perspective that the high precision permeability before and after the drilling fluid intrusion should be based on the pore structure has been put forward.Secondly,based on the Maxwell equation which is the response of the electromagnetic wave propagation resistivity logging to the layered medium,a new vector finite element approach has been used to research the forward simulation method of LWD induction resistivity and verify the accuracy,Construct S_phlshls and S_lhaphap by simulation results and make disciplines to determine invasion depth range.Twenty resistivity theoretical logging data which forward modeled by R_i,R_xo,R_t and the measured curve construct the least-squares objective function,Establish marquardt's method of LWD resistivity joint inversion to solve the issues of formation real resistivity and invasion radius.Realize formation resistivity non-invading inversion by LWD induction resistivity and mud invasion depth high accuracy and quantitative calculation in invasion condition,lead good effect in practice.At last,based on processed results of several wells,variation characteristics of time-lapsed LWD induction apparent resistivity and multivariate change rules of mud invasion radius have been constructed,which provides reference for the accuracy invasion depth calculation of lack data wells.Thirdly,through the NMR T2 spectrum data and capillary pressure data from the cores lab experiments,the pore structure of cores before and after mud invasion has been thoroughly analyzed.Based on the flow unit index FZI and Neutron-Density cross plots,the Fisher discriminant analysis method,neutron-density plate and support vector machines algorithm have been established to calculate permeability before mud invasion using the two conventional logging data.Timur-Coates and Swason parameters have been picked to calculate the NMR permeability and its accuracy has been validated through comparison.Through the comparison study of thirty-six NMT T2 samples before and after mud invasion,the correction models before and after invasion have been built and validated through the data excluded from the study samples.The non-invasion permeability inversion method is successfully achieved.Finally,a work flow for the formation damage has been built and applied to 11 wells and17 zones in the target area.The permeability damage ratio shows 76.5%agreement between the evaluation model and the actual result.The formation damage discrimination shows 100%agreement.The desired application effect has been achieved.