Abstract
The oil and gas field in Iraq, referred to as Field A, has demonstrated consistent hydrocarbon production from its cretaceous reservoirs since its inception. A comprehensive reservoir characterization workflow, integrating petrophysical, geological, and geomechanical modeling enabled extraction of important reservoir insights, faster and safer drilling, and optimum completion design maximizing production from this field. Acquisition of advanced acoustic data, along with high-resolution image data has been instrumental in reservoir characterization. High-resolution multi-shot processing of monopole & dipole data provided insights into the formation properties and their variation radially and laterally. Dipole shear anisotropy analysis helped recognize the presence of stress-induced and intrinsic anisotropy in the formations. Geological features could be modeled using a combination of dipole shear anisotropy and image interpretation results. The complex pore system in carbonates poses challenges for using empirical porosity-based permeability estimation methods, an innovative workflow for permeability estimation was developed, utilizing Stoneley attenuation to derive continuous permeability. This workflow was carried out for multiple wells of Field A drilling across the Cretaceous successions. Acoustic anisotropy was observed in some intervals in deeper cretaceous reservoirs. The direction of anisotropy was found to be NE-SW which is aligned with the regional maximum stress direction. Stoneley mobility was analyzed and calibrated with NMR and other reservoir measurements to identify high mobility zones. These results integrated with petrophysics, geology, and geomechanics led to the evaluation of the potential reservoir zones thus aiding in future production planning. Multi-well pore pressure and horizontal stress modeling workflows were utilized Heavily depleted areas of the field were then recognized as differential stuck intervals and development drilling plans were modified accordingly. Horizontal stress modeling was carried out to identify stress barriers in the tight reservoir to assess the feasibility of successful fracking operations. The minimum required bottom hole pressures (BHP) have been also calculated for the initiation and propagation of the hydraulic fractures. This paper demonstrates the value of multi-well study and integration of petrophysical, geological, acoustics, and geomechanical analysis to get critical insights on reservoir and completion quality for sweet spot identification and drilling new wells for better productivity. Recommendations generated from these workflows served as a catalyst for achieving ambitious production goals in the field.
