Formation Pressure While Drilling data verified with Wireline Formation Tester, Hibernia Field, offshore Newfoundland
Authors: Mishra Vinay Kumar , Haynes Frederick Mitchell , Pond Steven 
Published: February 2016

Pressure measurement plays a critical role in the development and management of compartmentalized reservoirs. Conventionally, pressure data have been recorded using wireline formation tester (WFT) tools. In highly deviated or horizontal wells, wireline testers must be conveyed on drill-pipe at considerable expense and often with operational risk and limitations.

To reduce operational risk and costs of long reach directional drilling of the Hibernia Field, offshore Newfoundland, a new generation formation pressure while drilling (FPWD) tool was deployed. To confirm the capability of acquiring quality pressures with mud-pulse based telemetry, the conventional wireline formation tester tool and the FPWD were run in the same well.

The pressure and mobility data recorded with the FPWD tool and wireline formation tester tool matched within 1 psi and with a fluid gradient difference of less than 0.004 psi/ft. Twenty-one successful tests were acquired in rocks with mobility ranging from 4 to 1100 md/cp. A pre-set testing sequence that never exceeded 15 minutes of stationary time was used. Seal integrity and tight tests could be readily identified from 6-bits per second mud-pulse telemetry. In addition to comparing pressure measurements, the FPWD tool was run both while circulating mud and with the pumps off. Although the pumps on test did introduce a fine scale noise, the pressure and mobility data collected were identical.

LWD and wireline pressure data were both collected in a second Hibernia well when the FPWD tool failed to seal with the formation after the fourth pressure measurement. These four pressure points repeated precisely when measured subsequently with wireline technology. The probe filter, which was the cause of the failure in the previous tests, was redesigned and several subsequent runs have been successfully completed at Hibernia with a 100% seal success. FPWD technology is now the preferred deployment mode when unassisted wireline runs are not possible.

Introduction

Discovered in 1979, the Hibernia oil field is located 315 km east southeast of St. John's, Newfoundland, in the Cretaceous sediments of the Jeanne d'Arc Basin1. In the first nine years of uninterrupted development, more than 53 wells have been drilled from the gravity-based Hibernia Platform. The majority target a 200m thick, reasonably high net to gross section of stacked and braided fluvial channels in the Hibernia Formation at average TVDss of 3900m. A smaller number of wells target the younger Ben-Nevis Avalon (BNA) shallow marine sands and estuarine reservoir units at approximately 2400m TVDss.

Multiple episodes of extensional tectonic activity created a complex fault compartmentalized setting for both the Hibernia and Ben-Nevis Avalon reservoirs2,3. For the most part, the development strategy has been, and continues to be, to complete producer-injector pairs in each fault separated reservoir block where mapping and economic evaluation justify development (Figure 1). In the southern portion of the Hibernia Reservoir, pressure and production is supported by water injection, while produced gas is injected in the northern blocks. The BNA is developed solely by waterflood.