Numerical analysis of the effects of downhole dyna

Authors: Dejia Di Guo Tao Bing Wang Xu Chen Jiming Sun

Publish Date: 2014/07/11

Volume: 11, Issue: 3, Pages: 391-400

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Abstract

Formation testing while drilling is an innovative technique that is replacing conventional pressure testing in which the fluid sampling is conducted in a relatively short time following the drilling At this time mud invasion has just started mudcake has not formed entirely and the formation pressure is not stable Therefore it is important to study the influence of the downhole dynamic environment on pressure testing and fluid sampling This paper applies an oilwater two phase finite element model to study the influence of mudcake quality and mud filtrate invasion on supercharge pressure pretest and sampling in the reservoirs of different permeability However the study is only for the cases with water based mud in the wellbore The results illustrate that the mudcake quality has a significant influence on the supercharge pressure and fluid sampling while the level of mud filtrate invasion has a strong impact on pressure testing and sampling In addition insitu formation pressure testing is more difficult in low permeability reservoirs as the mud filtrate invasion is deeper and therefore degrades the quality of fluid sampling Finally a field example from an oil field on the Alaskan North Slope is presented to validate the numerical studies of the effects of downhole dynamic conditions on formation testing while drilling

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