Title : Improved Interpretation of Laminated Formations in Mature Fields Using Calculated Rh and Rv Logs From Conventional Resistivity Measurements in Multiple Wells.
A new technique is presented which detects electrical anisotropy from conventional resistivity logs in multiple wells, allowing the user to identify laminated pay intervals and create horizontal and vertical resistivity curves.
The benefits of tri-axial resistivity data in laminated formations are well known and lead to interpretation results with very low uncertainties. However, many laminated reservoirs were logged before these tools become available and interpretations using conventional measurements are generally pessimistic and prone to very large uncertainty.
The electrical anisotropy of a formation is determined from changes in responses of conventional resistivity measurements in multiple wells with different angles of relative dip. Rv and Rh curves are computed from the conventional logs and these measurements are then used in a Laminated Shaly Sand Analysis.
Case study results are presented from low-resistivity laminated shaly sand pay intervals in South East Asia, along with some shaly sand intervals which are not laminated. This illustrates how the technique can be used to differentiate laminated formations from those which may be bioturbated or disturbed in some way.
The value of this technique lies in the fact that old fields containing laminated formations can now be re-evaluated in a way which confirms the formation type and allows results to be generated with low uncertainty. In cases where a small number of wells do have tri-axial data, this techniques provides a method for extending the tri-axial interpretation to the other wells, while also monitoring the changes in the laminated formations across the field.
Rick Aldred is a consultant petrophysicist with 37 years’ experience, including 15 years with operating E&P companies, 10 years with logging companies providing consulting services, 10 years in software development and 2 years as an independent consultant. He has worked in Europe, North Africa, The Middle East, The Indian Subcontinent, South East Asia and Australia.
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