First Multiphysics Integration of 3D Resistivity Mapping With 3D Sonic Imaging to Characterize Reservoir Fluid and Structural Elements
Authors:   SLB, Al-Lawati Redha , Viandante Mauro ,   SLB, Donald J. Adam ,   SLB, Eide Maren ,   SLB, Abdullah Ibrahim ,   SLB, Samir Eman ,   SLB, Millot Pascal ,   SLB, Al Shaqsi Amani ,   SLB, Al Badi Othman ,   SLB, Al Qassabi Fahad ,   Oxy Oman, Al Shaqsi Marwa ,   Oxy Oman, Al Hamadani Adil ,   Oxy Oman, Al Arafati Khalil ,   Oxy Oman, Johnson Clive ,   Oxy Oman, Hassan Khalil ,   Oxy Oman, Al Shukaili Jalal ,   Oxy Oman
Published: November 2024

Well placement and real-time evaluation of high-angle and horizontal wells is a well-established workflow that effectively ensures a consistent distance to the caprock and delineates sublayers within the reservoir. Contrasts in deep resistivity measurements are interpreted as changes to hydrocarbon saturation or formation composition. Wellbore images show layer boundaries and fractures that intersect the wellbore. Sonic imaging in the same environment provides information about contrasts in acoustic impedance associated with geological features such as structural and stratigraphic boundaries and the presence of natural fractures/faults. This paper will discuss how combining all three measurements provides rich insights to reservoir characterization in a horizontal well drilled through a carbonate reservoir. The integration of 3D resistivity mapping with 3D sonic imaging provides unprecedented reservoir insight. The 3D resistivity mapping is challenged by resistivity response to formation boundaries or fluid changes within the volume of investigated rock. Incorporating 3D sonic imaging with its sensitivity to lithological or stratigraphic boundaries and natural fractures provides a more comprehensive interpretation. There are three major discoveries within this case. There is a consistency of dip, azimuth, and distance to the caprock for both the acoustic and resistivity measurements; however, there is also a clear reflection from the bottom of the reservoir layer. The free-water level within the layer can be determined as the resistivity profile defines the saturation changes until the bottom boundary and potential oil-water contact. Secondly, there is correlation between steeply dipping or near-vertical acoustic reflectors running parallel to the well trajectory and the lateral changes in the resistivity profile on either side of the wellbore. This is interpreted as saturation changes laterally caused by the presence of near-vertical fractures or compartmentalized flow units due to the nature of the rock or existing baffles/barriers within faulted blocks. The third observation is the layering and heterogeneity within the caprock. The subtle resistivity contrasts and variable subhorizontal reflectors that vary with strike and dip. The convention of the caprock of being a homogenous unit is confronted by the measurements highlighting its heterogeneous and anisotropic nature. In a field with complex reservoir architecture (stratigraphy and fractures) and complex fluid relationships, the case study shows how the first multiphysics integration of 3D resistivity mapping with 3D sonic imaging enables: • Unbiased integration based on independent measurements to characterize reservoir features (fractures, lithology anisotropy, layering) • Validate interpretation in complex geological environments with structures remotely detected away from the wellbore • Fluid distribution understanding at reservoir scale as a function of structural features and stratigraphic elements • Novel input for properties distribution and reservoir dynamics as opposed to exiting geostatistical methods to model reservoir properties This case study represents the first multiphysics integration of 3D resistivity mapping and 3D sonic imaging to characterize reservoir fluid and structural/stratigraphic elements. The integration of all the measurements, along with borehole images, provides an innovative approach that helps to unlock full reservoir understanding.