ABSTRACT
Reservoir-X in field-A is a very tight marginal carbonate reservoir which has proven potential and recently undergoing development on many other fields in UAE. Motivation for the present study was to properly characterize the fractures contribution to reservoir productivity to assess the feasibility of reservoir development. Geological Data of the reservoir from drilled wells and observation from cored wells show the presence of natural fractures in the reservoir.
Multidiscipline data gathering and evaluation has been carried on 26 wells and 6 cored wells. These include borehole image evaluation (wireline and LWD), stoneley and advance deep shear sonic evaluation, core observation, routine core analysis, production test, seismic attribute analysis, regional geology and drilling events analysis.High resolution LWD Micro-resistivity Formation Image over 3200 ft in the horizontal section was acquired, processed and interpreted. Advance acoustic deep shear image and stoneley fracture analysis from three wells were performed and compared to the same wells where core CT scan and image logs were acquired to evaluate the fractures propagation away from the borehole. This information was used to interpret fracture type, fracture orientation & computation of fracture attribute.Core observation was conducted on seven cored wells by using visual inspection, whole core CT scan, dual energy plug CT scan, thin sections and routine core analysis data. The data is depth matched and then integrated with the log data.
Detailed fault interpretation was done on 3D seismic data in the region of interest. 3D variance & curvature attributes were generated on conditioned seismic data for edge detection and was further used to extract the Seismic Discontinuity Planes (SDPs). Extracted SDPs were carefully analyzed with respect to the orientation of fracture present in the wells
All events of drilling breaks, bit drop, abrupt loss of drilling mud from drilled wells were recorded and analyzed to support fracture identification, particularly at the un-cored wells or in the case of image log absence. Production tests from some appraisal wells provide indication of fracture productivity.
The fractures were then classified based on process origin, their attributes and ranked accordingly to their potential contribution toward production.
The study confirmed that reservoir-X has two main reservoir zones with different fractures intensity and attributes due to their distinct mechanical properties.
Some open fractures were observed but the potential contribution to production is yet to be validated by more comprehensive dynamic data. The study result become basis for planned PLT and DST.
