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Drilling Evolves as Exploration Campaign Moves to Deeper Water Offshore Mexico

Topics: Offshore

During the 10-year period between 2003 and 2013, Mexico drilled 30 deep- and ultradeepwater wells in water depths ranging from 512 to 2900 m. During this exploration period, the learning curve has improved with each subsequent level of difficulty and increased well depth. In order to reach water depths greater than 1500 m, both the wellbore geometry and the real-time data-acquisition strategy have changed.

Introduction

Fig. 1 shows how wellbore geometry evolved to reach geological targets and how the various hole diameters changed to meet exploration objectives. As seen on the left of the figure, a conventional drilling and data-acquisition approach was applied: drilling a 12¼-in. pilot hole for data acquisition and thereafter enlarging the hole to 17½ or 14¾ in. to set the casing. This enabled real-time ­logging-while-drilling (LWD) data acquisition and provided a 12¼-in. maximum hole size for wireline data acquisition. However, as water depth increased (right side of Fig. 1), the hole-size requirements for the mechanical well design increased accordingly. In some cases, with shallow geological targets, the required hole size of 22 in. was needed for the casing. This required a strategy to drill an appropriate hole size for LWD and wireline evaluation with minimal dedicated drilling and hole-enlargement trips. The evaluation programs considered real-time data needed to make decisions during the drilling phase and support decisions for a more-­comprehensive wireline evaluation program if the zones warranted more extensive evaluation. The comprehensive evaluation logging suites included ­wireline-logging tools with triaxial resistivity, elemental-capture spectro­scopy, nuclear magnetic resonance, vertical seismic profiles, mechanical sidewall coring, and the complete suite of formation-testing services for pressure and fluid sampling. The ultimate goal of the program was to provide accurate volumetrics, physical rock samples, and fluid samples for the booking of hydrocarbon reserves.

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 25030, “Drilling Evolution of the Ultradeepwater Drilling Campaign in Mexico, Perdido Fold Belt,” by Victor G. Vallejo, Aciel Olivares, and Octavio Saavedra, Pemex, and Juan R. Lopez and Manuel E. Torres, Schlumberger, prepared for the 2014 Offshore Technology Conference Asia, Kuala Lumpur, 25–28 March. The paper has not been peer reviewed. Copyright 2014 Offshore Technology Conference. Reproduced by permission.
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Drilling Evolves as Exploration Campaign Moves to Deeper Water Offshore Mexico

01 May 2015

Volume: 67 | Issue: 5

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