Improves Vertical Coverage and Well Performance in the Lost Hills Field
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Challenge | Solution | Results | Benefits
Industry Challenge
| Underachieving wells are common place. Improving sustained production while consistently creating discrete fractures in cased and cemented wellbores (vertical or horizontal) has, historically, proven to be a challenge. Flow convergence is also a common issue, especially in the near-wellbore region, and is a result of poor conductivity within the fracture. Traditional multi-stage fracturing treatments include the common “perf-and-plug” method. This technique requires multiple trips in and out of the well to accomplish individual components of an overall fracture-stimulation completion. Perf-and-plug uses a perforating assembly to initiate a fracture by using shaped explosives. Once the perforation has been created, the assembly is run out of the hole and the wellhead is rigged up to pump trucks so that proppant can be injected into the fractured zone. Once completed, the pumping equipment is detached and a new perforating assembly coupled with a mechanical plug is run into the hole and set to isolate the treated zone from the next highest zone targeted for stimulation. There, the perforation assembly is triggered to initiate a fracture in the new target zone, which is run back out of the hole to allow for the pumping of proppant into the fracture. This process continues until all zones within the well have been treated. Although the perf-and-plug method has proven results, it is both time consuming and costly. |
Halliburton Solution
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Halliburton's pinpoint stimulation services are single-trip alternatives for completing multi-zone wells. Pinpoint stimulation represents a variety of methods for stimulating multiple zones in wells by perforating, fracturing, and diverting fluids in a single trip by starting at the lowest zone and working up to upper-most zone, treating each zone on the way up. All pinpoint stimulation services are based on established technologies including Hydra-JetSM service perforating, coiled-tubing and hydraulic-workover processes for working with live wells, proppant fracture treatments where a bridge plug and packer are used to isolate preperforated intervals, and annulus fracturing.
Halliburton's CobraMax service, a key pinpoint stimulation-services technology, has been designed to create efficiencies during the multi-zone completion process and thus overcome issues associated with the standard perf-and-plug treatment while maintaining all the advantages of fracture stimulation. Similar to the standard perf-and-plug method, CobraMax uses a coiled-tubing bottomhole assembly (BHA) deployed in the well for fracturing purposes; however, this technology only requires one trip into the well. The coiled-tubing BHA, once run into the furthest-most zone, uses the Hydra-Jet service to initiate a fracture. Hydra-Jet service takes advantage of jetting fluids at extremely high pressures through the casing and into the formation to create a perforation; this method is less damaging to the formation than the use of explosive-jet perforation and is far less dangerous. Stagnation pressure, which is the combination of annulus pressure plus pressure resulting from the conversion of the high-energy jet stream to pressure, extends the fracture at the jetting impingement points. Proppant is then run into the well to the fractured zone using the same assembly, eliminating a trip out and back into the well. This is then followed by a sand plug to isolate the zone. After the first zone has been treated and plugged, the coiled-tubing BHA moves up slightly past the second zone to wash it down. From there, the process is repeated, all without ever running the BHA up out of the well.
CobraMax service is a unique technology in that it also addresses common flow-convergence issues. This service uses a specially-engineered proppant pack that increases conductivity of hydrocarbons from the fracture to the wellbore, ultimately increasing production. Flow convergence can be compared to a busy highway with several lanes being diverted to one lane during rush-hour traffic. Cars inevitably pile up, causing a traffic jam. As more lanes open up, the slowdown subsides, allowing cars to pass freely. In the same way, the proppant pack used with CobraMax service has been designed to essentially provide more “lanes” for the hydrocarbons to flow through, thus preventing radial flow convergence.
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Operator Results
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In 2004, a major operator in the Lost Hills Field of Northern California held a frac-off competition in which several service providers competed to become its preferred provider. Each service provider was given 18 wells with the same parameters in the same area, and their goal was to provide the best return for the operator, demonstrating both long-term production and long-term costs. The decision as to which service company would become the preferred provider was based on safety and cumulative production performance over a 6-month period.
Halliburton's CobraMax service went head-to-head with the competitors' use of the standard perf-and-plug treatments. After six months, results showed that wells treated with the CobraMax service outperformed other wells by as much as 40%. Although costs proved to be slightly higher with the CobraMax service, it was found that the cost per barrel of oil produced was significantly lower, leading the major operator to choose Halliburton as its preferred provider.
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| Operator Benefits |
CobraMax service can provide an operator with the following benefits:
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Eliminates the need for mechanical plugs that would have to be removed later
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Uses Hydra-Jet technology for initiating fractures as opposed to the risky explosive-jet method
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Enables operators to make only one trip into the wellbore, as perforating and fracturing can be accomplished in the same trip
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Optimization of the diversion process
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No temperature limits with the bottomhole assembly
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Reduces wellbore damage with continuous operations in one trip
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This RedTech paper summarizes SPE 101840 “Extreme Multistage Fracturing Improves Vertical Coverage and Well Performance in the Lost Hills Field” by C.W. Glatz, SPE, and J. Luna, SPE, Halliburton, and K.A. Hejl, SPE, A.M. Madding, SPE, and M.F. Morea, Chevron North America E&P Co.; paper presented at the 2006 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 24-27 September
For more details on this paper or product, email us at stimulation@halliburton.com.
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