[M-IS18] Drilling Earth Science

[MIS18-P10] Determination of In-Situ Horizontal Stress Direction and Magnitude Using Conventional and XRMI logs: A Case Study in Zagros Suture Zone in Northern Iraq.

*Nazir mafakheri bashmagh ¹, Weiren Lin ¹, Foad Yousefi ² (1.Kyoto university , 2.Soran University )

Keywords:Tectonic movement , In situ stress , maximum horizontal stress , Image logs , Breakout, Drilling Induced Fracture

Arabian and Eurasian plates collision zone is one of the seismically active within the Middle East region. The northeastern part of the Arabian plate is placed in northern Iraq that encompasses a suture zone with the Iranian plates called the Zagros suture zone. In the past twenty years, several oil wells had been drilled in the suture zone nearby. Due to the complex nature of geology and lack of reliable geomechanics data, oil companies face drilling, well completion, and production problems in this area. As such, there is a great value in geomechanical study and one key element of any successful geomechanical study is the proper determination of magnitude and orientation of principal in situ stresses. The deepest drilled formation in this study is the Albian upper Qamchuqa Formation in northeastern Iraq which is a carbonate hydrocarbon reservoir containing significant natural fractures. Based on the faulting system, the stress regime is varying between strike-slip and thrust fault around both flanks of the suture zone in this area. In this study magnitude and orientation of maximum horizontal stress (σ_H) and minimum horizontal stress (σ_h) determined by using high resolution X-tended Range Micro Imager (XRMI) and conventional log for two oil wells. Below the 1590 TVD, a high number of breakouts (BO) with considerable length and few drilling-induced fractures (DIF) were observed in the well A and also few numbers of BO detected in the well B. Detected BO showed low standard deviation and varies from N10^oW to N10^oE. The average E-W direction of the maximum horizontal stress determined by BO and DIF shows relative consistency with the direction of NE-SW to E-W tectonic movement base on the world stress map (WSM) in the nearby Zagros suture zone and also with earthquake focal mechanism solutions in a previous study. In the last step, the magnitude of vertical stress (σ_v), horizontal stresses (σ_H, σ_h)_, and pore pressure (P_p) has been determined by density, sonic, XRMI, and repeated formation test (RFT) respectively. In the end, I would like to express my gratitude and appreciation to Schlumberger Japan for providing Techlog Software for this research.