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Case Study: Reduce Well Construction Time and Cost



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(Left) The project was completed within AFE despite a rig evacuation due to Hurricane Rita. (Right) Extending setting depth for the 9 5/8-in casing eliminated the need for the planned 7 3/4-in liner, reducing cost, complexity, and NPT.


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The pore pressure model was updated in real time as data was acquired.


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Schlumberger 3D mechanical earth model, developed using US Minerals Management Service (MMS) checkshot data, enables geomechanics engineers to extract a look-ahead pore pressure model. This, coupled with PERFORM pore pressure interpretation and wellsite information, reduces uncertainty in the pore pressure prediction at the bit, as well as the risk of wellbore instability, kicks, and influxes, and allows optimization of casing points.

PERFORM real-time pore pressure management helps Chevron optimize Gulf of Mexico well construction

Challenge
Optimize construction of directional, shelf deep gas well with narrow mud weight window between estimated pore pressure and formation fracture gradient.

Solution
Model, monitor, and manage pore pressure in real time.

Results
Successfully set 11 7/8-in casing 600 ft deeper and 9 5/8-in casing string 1,000 ft deeper than preplanned model, eliminating need for 7 3/4-in liner. Completed project within AFE despite rig evacuation due to Hurricane Rita.

Modify casing program on the fly
Chevron's plan for constructing a directional, shelf deep gas well in its Fiesta 2 project in the Gulf of Mexico, West Cameron Block 42, called for setting 11 7/8-in casing to 10,802 ft, 9 5/8-in casing to 15,510 ft, and a 7 3/4-in liner from there to total depth. Use of the pore pressure model derived from the Schlumberger Gulf of Mexico pore pressure cube and the PERFORM Performance Through Risk Management Process—together with the close teamwork of Chevron, Schlumberger, the mud logger, and the rig crew.allowed modification of that plan to optimize well construction as drilling proceeded.

Real-time pore pressure management enabled the team to set the 11 7/8-in casing 600 ft deeper than the preplanned model and extend setting depth for the 9 5/8-in casing by 1,000 ft. This eliminated the need for the 7 3/4-in liner, reducing cost, complexity, and nonproductive time (NPT).

Update pore pressure model in real time
Chevron's predrill pore pressure result was refined from the Gulf of Mexico pore pressure cube created by Schlumberger. The real-time pore pressure model helped the team keep mud weight in the narrow window between estimated pore pressure and the formation fracture gradient.

During well construction, the model was revalidated and calibrated in real time using sonicVISION sonic-while-drilling tool data, rig-site analysis of physical indicators, and data from two major events—a kick at 12,735 ft and a small fluid influx at 14,528 ft.

Achieve drilling objectives within AFE
Teamwork, the predrill pore pressure model, and the PERFORM process, which was provided through a Schlumberger Operation Support Center, helped control and minimize the severity of drilling events and pushed the casing points. The Fiesta 2 project was completed within AFE, and all drilling objectives were met. On the Fiesta 1 well, the TD objective was not reached, due to earth model uncertainties and ensuing hole problems. Lessons learned from the Fiesta 1 well were applied by PERFORM engineers on the Fiesta 2 project.

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