Roy Nurmi¹, A.J. (Tony) Lomando², B. Katz³

(1) Borehole Geology & Technology, Fallbrook, CA
(2) Chevron Petroleum Technology Company, San Ramon, CA
(3) Cabinda Gulf Oil Co

ABSTRACT: Status and Future of Carbonate Formation Evaluation Using Well Logs

Pay determination, water saturation and porosity, the routine objectives of well logging today, are generally not enough information with which to plan reservoir development or predict recovery. Past experience demonstrated that overly optimistic recovery predictions along with poor development planning occur if reservoir barriers and compartmentalization as well as high permeability paths, such as open fractures and faults, are not defined early within a reservoir characterization evaluation plan. These features need to be identified by well logs so that they can be extrapolated throughout a reservoir. Moreover, rapid and efficient evaluation and development of new carbonate discoveries and field acquisitions requires thorough formation evaluations to guide assessments and major investments. Cyclo and sequence stratigraphy are now basic tools from developing high resolution layer models for reservoir characterization and simulation. Lithology from logs will continue to develop as a robust tool for interpretation of sedimentary cycles and sequences to bridge the gap between cored and uncored wells within the reservoir. An improved understanding of all new promising technology and measurements is needed for future reservoir characterization, although it is very likely that an integration of all measurements and data will still be required to approach an acceptable reservoir assessment or characterization. The integration of new advanced high-resolution NMR logging with 3-D borehole imagery and a more thoroughly defined 4-D invasion profile will be keys for more realistic and predictive carbonate formation evaluation. This data will be used to guide well testing and/or completion efforts while wireline production monitoring will be needed to refine early simulation models. Most important, the industry must resist the pervasive pressure for short-term cost savings and develop cost-effective approaches to formation evaluation, which will include an increased use of logging while drilling technology especially for major projects and the routinely undersampled deep prospects.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado