The Eagle Ford shale in south Texas is the one of the most recent developments in unconventional reservoir exploration. Numerous existing completion methods have been applied in this nano-darcy formation with various degrees of success. The horizontal Eagle Ford wells in the northeast area of the current Eagle Ford play (DeWitt County) require a completion strategy that is reservoir specific. The production in this area has a high liquid/gas ratio and presents different challenges for commercial development than those in the typical “high-rate water frac” completions associated with dry-gas shale stimulation theory. Previous high-rate water frac completions in this area typically associated with the “Barnett-style shale stimulation” achieved poor results. Core analysis shows that a low Young's Modulus (YM) (soft rock), high clay content, and the potential for high liquid-hydrocarbon production require the need for a different completion strategy. Swelling formation clays and proppant embedment were formation issues to consider along with the multiphase hydrocarbon production. Higher conductivity fractures would be required, but various unknowns existed: How many frac stages should be pumped?How much proppant should be pumped on each frac stage?What type of proppant should be used?What mesh proppant should be used?What perforation scheme was needed?What type of completion fluids should be used?What injection rate was needed?How would fracture-injection issues be handled? This paper discusses how a collaborative, engineered approach was applied to the completion of the Eagle Ford shale to deliver a commercial asset. To address the unknowns, the methodology included geologic and reservoir understanding applied to the stimulation design and execution. The stimulation resulted in hydrocarbon production that exceeded expectations. Comparative well results will be discussed.
Anadarko Petroleum's Marco Polo development is located in approximately 4,300 ft. of water in Green Canyon Block 608, in the central Gulf of Mexico (GOM). The discovery and appraisal wells were drilled in 2000, and the field will ultimately be produced using a tension leg platform (TLP). The development drilling, which will be complete by 1st Quarter 2003, uses several innovative approaches to maximize project value. Some of the approaches challenge current industry trends and will be highlighted in this paper. Introduction Over the past decade, multiple fields in deepwater GOM have been developed and the region remains one of the frontier exploration areas of the world. The challenge of the Marco Polo development is the same as with most projects - to deliver maximum value. What makes this project unique is the approach. The first step was to evaluate the major components to determine the most appropriate use of current technology. Those selected technologies that significantly challenge current industry trends include: Rig Selection. The rig selected to drill the development wells is an Express-Class, dynamically positioned fifth generation semi-submersible with enhanced pipe handling capabilities. Drilling Fluid System. A newly developed water-based mud (WBM) was used in lieu of the synthetic-based drilling fluids (SBMs) traditionally used in the GOM. Cement Design. To address shallow water flow concerns, a non-foamed slurry was used on the conductor casings instead of foamed cement-the predominate slurry for cementing conductor casing in shallow water flow areas in the GOM. Additionally, a flexible slurry was used on the production casing to mitigate annular pressure buildup (APB). Both of these slurries are new developments in technology. Casing and Wellhead Design. The casing design was optimized from the exploration wells and drew on recently published casing failures in deepwater GOM1. Subsea wellheads were used and will be tied back to the surface once the TLP is installed. To meet the design criteria, the wellheads included a "thick wall extension" below the 18 3/4-in. high-pressure wellhead housing (HPWHH). The 36-in. low-pressure wellhead housing (LPWHH) and casing above the mudline was also externally insulated for flow assurance reasons. Rig Selection As with all drilling projects, rig selection plays an important role in success - particularly with batch set operations. Key issues related to rig selection for the Marco Polo project included:The ability to work in high current environments. Immediately prior to beginning the drilling program, a fourth generation, moored semi-submersible had drilled a well in an offset block where loop currents were present. As a result of these high loop currents, the drilling operation was suspended a total of 21 days.Enhanced pipe handling, which could add significant value during batch set operations.Variable deck loadLiquid mud storageBulk storage (cement and mud)Hydraulics Once qualifications were set, the rig list was narrowed down to two rigs;a fourth generation moored semi-submersible that had been used to drill the discovery and delineation wells and an immediate offset; anda fifth generation dynamically positioned (DP) semi-submersible with enhanced pipe handling capabilities. Because a batch set operation was planned, the fifth generation rig's increased variable deck load, additional bulk storage, and enhanced pipe handling capabilities delivered improved performance over the fourth generation rig. These features, combined with DP capabilities, established the fifth generation rig as the optimal choice.
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