Cont. from page 6, Hydraulic Fracturing....

Halliburton described its CobraMax and SurgiFrac options for pinpoint stimulation. With CobraMax, holes are jetted in the casing, the frac is pumped down coiled tubing and the annulus, sand is filled and operations move uphole to the next zone. Describing a Chevron program in California's Lost Hills Field, Halliburton noted that, looking at results from over 30 wells, completion costs/BOE were down by almost half compared to conventional perf and plug limited-entry fracturing. These completions averaged 17 fracs per well. This technology is also being used in horizontal wells with Halliburton noting Barnett Shale applications.

There was a final caution from the experts. There is this picture in our

minds of a single fracture growing in a single plane, oriented perpendicular to the least in-situ principal stress with fluid and proppant moving in a piston-like manner inside the fracture. The fluids going in last will be those coming out first. Industry is increasingly recognizing that the real world is not that neat. There can be multiple fractures, multiple planes, branching, fractures growing erratically, etc. The result is that fracture width, length, height and flow capacity are often significantly less than designed. Fracturing pressure can be higher than predicted. During flowback there can be a mixture of fluids/proppant sizes rather than the expected last in/first out. Production declines are often higher than expected. Post-frac

buildup data look like radial flow, causing one to question "Where's the frac?" Off-balance growth and fracture complexity are the answer.

Off-balance growth tendencies can be reduced by adjustments in treatment design, perforating scheme and the details of job execution. Multiple, limited entry sets of perfs are common practice, but there is increasing industry recognition that fluid energy should be even more focused—pinpoint, properly oriented perforation and stimulation. This minimizes multiple fracturing and fracture complexity/tortuosity, which means pumping pressure is less and longer primary fractures can be achieved.

Independents’
Perceptions of Most Beneficial Technologies

Each year in their January issue, The American Oil & Gas Reporter surveys a segment of its readership, one of the questions being, which technologies they perceive will be most beneficial to them. Although not a rigorous statistical process with hundreds responding, perceptions are still insightful. Perceptions from all respondents covering all categories are shown. Recognition of fracturing/stimulation technology is near unanimous. Only oil-well drillers considered another technology more beneficial, in their case it was seismic/geophysics that received their top ranking. Horizontal/directional drilling was ranked the third most beneficial technology by every category except the small-driller category. Workover/well servicing and logging/formation evaluation had their audiences.

Most Beneficial Technologies
(All Survey Respondents)

Graph reprinted with permission