Finite Difference Modeling for Wellbore Stability Analysis in HPHT and Inclined Conditions
Bidin, Lufti Abbas
Engineering Honours Degree, 2006
University of Adelaide
This honours project titled “Finite Difference Modeling For Wellbore Stability Analysis in HPHT and Inclined Conditions” is done to experiment the wellbore stability prognosis in some of the harshest well operation environments in the industry namely high pressure high temperature (HPHT) and inclined well conditions. The experiments or modeling activities are done using the 3D finite difference numerical modeling software FLAC3D developed by Itasca Consulting Group. Problems discussed in the literature concerning the afore-mentioned harsh conditions are addressed and modeled. An inherent problem for HPHT wells is limited mud weight window. The modeling done clearly shows this problem as well as giving insight on how to counter it. HPHT conditions also affect completion design by amplifying the strain increment in cement. The experiments by varying the cement Young’s modulus and Poisson’s ratio are done to model this problem. The modeling concurs with the literature in determining the cement properties as well as depicting the magnitude of changes brought about by the cement property variations. An inclined well is sensitive towards wellbore direction as well as the stress regime it is in. This honours project investigate inclination effect on a well in slightly inclined (6o) and most inclined (90o) conditions. The modeling activities done enable us to determine the best orientation for drilling an inclined well given the stress profile of the area as well as the desired inclination magnitude. Apart from the modeling experiments, this honours project also present a very extensive literature review on the area of wellbore stability. The literature review touches from the most basic concepts in rock mechanics such as stress-strain relationship to complex 3D modeling methods used to model wellbore stability. This honours project also validate the 3D modeling method using the FLAC3D software with two 2D methods, the 2D type curve boundary element method and the Kirch equation. The validation is important since the two 2D methods are well embraced and widely accepted as the rule of thumb in stress analysis in rock mechanics. Future modeling works especially using FLAC3D recommended in the area of wellbore stability for HPHT and inclined conditions include the coupling of thermal and mechanical effects for HPHT wells and a wider range of inclination angles for the inclined wells.