Presenter
Sergey Gavrik from Halliburton
Co-authors
Nigel Clegg, Karol Riofrio Rodriguez
Abstract
Title: Mapping Complex Oil Water contacts with Ultra-deep Azimuthal Resistivity, case studies from a Massive Carbonate Reservoir
Objective / Scope
Mapping the position of oil water contacts (OWC’s) and their displacement by production and water injection is crucial for understanding reservoir development, planning well trajectories, navigating within remaining hydrocarbon zones and setting completions. In a mature field with a long history of water injection and production, OWC’s are expected to be complex, in part due to depletion near to production wells but these mechanisms are not exclusive, and other geologically driven factors such as faults, sealing fractures and lithology can create complex sweeping scenarios.
Historically, OWC’s have been picked, mapped and prognosed using mainly well logs and other near wellbore inputs. However, the number of wells and the depth of investigation (DOI) of most Logging While Drilling (LWD) tools limits the interpreted area. The introduction of Ultra-deep azimuthal resistivity (UDAR) tools increases the volume of reservoir interrogated revealing complexities particularly in highly fractured/faulted zones where water injection can be directed by the subsurface structure.
Methods, Procedures, Process
UDAR technologies with a DOI in the region of 100ft+ expand the distance from the wellbore that OWC’s can be mapped. Inversion of this data greatly reduces the uncertainty, utilizing its ability to map multiple boundaries helping to understand variability in flooding. Despite this advancement, in the early stages of development Deep and UDAR inversions operated in 1D (pseudo 2D) mode, ignoring lateral variability. In non-layer cake environments, lateral features are incorporated in the 1D solution causing distortion to the inversion. The introduction of 3D electromagnetic inversion provides mapping capabilities in three dimensions, resulting in the ability to map the complex distribution of fault bounded OWC’s and enhancing reservoir understanding.
Results, Observations, Conclusions
Three studies are presented: The first one utilizes a deep azimuthal 1D inversion spanning 8 m from the wellbore. It reveals the movement of water in a vertical direction and isolated blocks of hydrocarbon, suggesting lateral movement of the fluids is constrained. Thus, the OWC’s are controlled by two mechanisms, faulting and lithology.
The second study investigates a mature carbonate with a variety of subseismic dislocations acting as baffles. 3D resistivity inversion made possible a detailed analysis of structural complexity in a comprehensible way through 3D visualization. Inversion results are independently validated to demonstrate the accuracy of the results.
The last study focusses on identifying hydrocarbon pockets left behind in a narrow target identified from seismic modelling, 3D EM inversion helps to limit the uncertainty of hydrocarbon distribution.
Novelty or additive information
OWC’s vary in their complexity from simple horizontal planes to highly variable 3D fluid distributions where affected by complex fault systems. The advancement of EM propagation tools in recent years has made it possible to invert for the structure in 1D and 3D to reveal their distribution.
The case studies reveal the possibility of mapping complex OWC’s with high confidence, verifying the results of the inversions by a variety of methods beyond just statistical analysis.
Biography
Sergey Gavrik, holding BSc in geology from Novosibirsk State University in Russia (2004). Joined Halliburton in 2006 as M/LWD field engineer. In 2012 transitioned to geosteering role, supporting Russia and Middle East operations. Currently serving as Technical Advisor for Halliburton geosteering operations in ConocoPhillips Skandinavia (Norway).