oa Generation of in-Situ Stress Map in Gulf of Suez (GOS) and Its Impact from Drilling High Angle Wells, Egypt

The effect of magnitude and pattern of earth’s in situ stress is generally manifested on the shape of the<br>borehole in a drilled well. It is well known that the stress around the wellbore causes deformation<br>depending on many factors ranging from rock strength to the deviation of the wellpath.<br>In this paper, a stress map is generated from borehole breakout along with other wireline logs from a<br>reasonably large database. Both vertical and deviated wells covering major part of GoS are considered<br>for this study. The fact that stress related breakout originates from the maximum tangential stress is<br>the main criterion here. The tangential stress is combination of forces like earth in situ stresses, drilled<br>mud weight and pore-pressure of the formation. Complimentary to the magnitude, breakout<br>orientation indicates the direction of minimum in situ stress in case of vertical wells. Stress evaluation<br>in deviated wells requires multiple well input in a limited area to generate a stress tensor diagram that<br>determines stress orientations with confidence. In a deviated well the breakout direction is controlled<br>by in situ stress with respect to the trajectory of the well. The study reveals that the min horizontal<br>stress (Sh) in GoS is aligned along two major trends. First, the main NNE - SSW trend, with an<br>average orientation of 10degN exists in most of the part. The second trend is aligned NE - SW and has<br>been observed locally at the central eastern and south-western part of GoS, with an average<br>orientation of 50degN. Most studies of the structural and tectonic history of the GoS have concluded<br>two age significant orientations for this extensional rift. The early to middle Miocene rifting, yielded Sh<br>direction of 55-60degN (rift-climax phase). The younger stress fields of the Late Miocene and Pliocene<br>times rotated progressively counterclockwise and yielded a 15-25degN direction that persisted into<br>early-late Pleistocene time. The main trend therefore is mainly controlled by this younger stress field of<br>the GoS rifting.