A particular South Texas gas field has suffered severe production decline in the last two years. The wells were completed in the Wilcox formation, which extends from the Burgos Basin in Mexico through Texas into Louisiana. The object was to identify and treat potential producing zones in all existing wells to increase production. Hydraulic fracturing is the preferred stimulation technique in these formations. Typically multiple zones are fractured in each of the wells. The stimulation treatments are designed with the aid of 3D hydraulic fracture models. Wireline logs provide the most comprehensive and continuous input parameters in such modeling for borehole stress profile, permeability index, elastic moduli, lithology, porosity and fluid saturation's. Existing open-hole wireline logging data were reprocessed using a new technique which provides all the available logging data in a format suitable for direct input in 3D hydraulic fracture models. An automatic zoning technique divides the data into consistent intervals based on stress contrast. The representative design parameters are then computed for each zone. The outputs are a blocked stress profile and a set of zoned fracture design parameters.

This new technique was used to evaluate all the stimulation candidates in the field. One well was bypassed for treatment altogether, saving $500,000 to $700,000 on a stimulation that would have had a marginal result at best. In another well, the log was used in combination with a Fluid Efficiency Test (FET) and a Step Rate Test to show essentially no leak-off, and hence very low permeability in one zone. This lower sand was skipped, and upper zones were fractured to increase gas production from 550 MMCF/D to 1,300 MMCF/D.

You can access this article if you purchase or spend a download.