Case Histories - Combining Crossed Dipole Sonic Anisotropy and Oriented Perforating To Optimize Hydraulic Fracturing In the Burgos Basin - Reynosa Mexico

Abstract

Proposal Based on local experience, a well-accepted work flow or set of best practices has been developed for optimizing stimulation treatments in the Burgos Basin. Recently, these best practices have been enhanced by combining stress field orientation and gyroscopically oriented wireline perforating. Orienting perforations in the direction of maximum horizontal stress has greatly reduced near wellbore tortuosity and friction in hydraulic fracturing treatments. The result has been improved proppant placement resulting in higher proppant conductivity and increased production. The best practices for optimization of the stimulation design and economic modeling include many steps. 1,2,3,4,5,6,7,8,9,10 The candidate selection process evaluates the net-to-gross sand thickness ratio, reservoir pressure, and permeability for each zone. The net-to-gross ratio provides information on productive and non-productive fracture height, which is needed for inflow analysis. The reservoir fluid, pressure, and permeability of the formation are vital for determining the fluid leakoff/fracturing fluid rheology requirements and required fracture conductivity. Geological and geophysical data are reviewed to identify potential reservoir boundaries such as faults or pinch-outs that could impede hydraulic fracture propagation. The vertical stress profile between the zone to be treated and the underlying and overlaying formations is used in 3D fracture simulators to evaluate the fracture height (and any possible unwanted outof- zone fracture height) versus fracture half-length and proppant concentration. To implement the oriented perforating enhancement to the best practices crossed dipole sonic anisotropy analysis is used to determine the far-field stress orientation and magnitude combined with the six electrode dipmeter for orientation and ovality visualization. Borehole breakout analysis and anelastic strain recovery of whole cores can provide near-field stress orientation data. These factors are then used to determine optimum perforation direction. In this paper, several case histories will be presented comparing the results of stimulation treatments using the normal practices and traditional perforating methods versus stimulation treatments using the same practices but incorporating oriented perforating. Stress Orientation and Borehole Breakout The near field stress orientation can be determined from borehole breakout analysis, which requires at a minimum multi-axis calipers and borehole orientation data. In both vertical and deviated wellbores, borehole breakout analysis from X-Y caliper data can sometimes provide suitable information. The borehole ovality can also be a result of the drill string and its rotation or sliding on the low side of the borehole in deviated well conditions. Both of these phenomenon can result in a key shaped borehole. If only X-Y caliper data is used, the pipe groove/key shaped borehole can be interpreted as borehole ovality. These conditions can generally be identified with the long axis of the borehole, constantly aligned with high side-low side of the borehole. Multi-axis calipers with more than X-Y measurements (Fig. 1) provide additional data which can enhance the borehole geometry-borehole break out analysis. Borehole imaging data (Fig. 2), ether ultrasonic or electrical, have much greater radial and vertical sampling than multi-axis caliper data. The imaging data not only provide high resolution borehole geometry data, but yield essentially a picture of the detailed bedding. Fractures can readily be identified from imaging data.