Application of the dc-Exponent Method for Abnormal Pressure Detection in Ahwaz Oil Field: A Comparative Study

Abstract

There are different methods for detection of abnormal pressure during drilling; one of these methods is the dc-exponent method. In this research, the applicability of the dc-exponent method is investigated for the detection of abnormal pressure zones in Ahwaz oil field in Iran.

Two procedures exist to calculate the amount of abnormal pressure from dc-exponent data: the Rehm-McClendon and Zamora methods. In some oil fields around the world just one of these methods is applicable and the other one provides incorrect results or is inaccurate. Therefore, in this work both methods are applied to six wells in Ahwaz oil field and a comparison is made between the real pressure (detected on the rig) and the results obtained.

Keywords:

• abnormal pressure
• dc-exponent
• drilling rate
• Rehm-McClendon method
• Zamora method

Notes

^a“Because the logarithmic term in g_p (pressure gradient) in subnormal conditions becomes negative and logarithm of negative numbers is undefined, so the amount of subnormal pressure cannot be determined by this method.” g_p = 7.65* log[(d _mod) _n − (d _mod )] + 16.5.