Integrating FPWD Measurements With Managed-Pressure Drilling
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 156888, ’Demonstrating the Value of Integrating FPWD Measurements With Managed-Pressure Drilling To Drill Narrow Mud-Weight Windows Safely in an HP/HT Environment,’ by L. Umar, SPE, I. Azian, N. Azree, and A.R.M. Ali, Petronas, and A. Waguih, SPE, F. Rojas, SPE, S. Fey, SPE, B. Subroto, SPE, B. Dow, and G. Garcia, SPE, Schlumberger, prepared for the 2012 SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, Milan, Italy, 20-21 March. The paper has not been peer reviewed.

A high-pressure/high-temperature (HP/HT) exploration field in Block PM on the northern side of the Malay basin, Malaysia, is notorious for a steeply rising pressure ramp, narrow drilling-operation window (only 0.5 to 0.6 lbm/gal in the 14¾ and 9½-in. sections), and interbedded sand/coal and shale formations. Block PM is still in the exploration-and-appraisal stage; therefore, petrophysical information is limited. Well SBD-2 was the second attempt to reach and cross the F and H sands. Formation-pressure-while-drilling (FPWD) and managed-pressure-drilling (MPD) technologies were applied to drill this well. FPWD provided a direct pressure measurement while drilling to set the lower boundary, and formation-integrity tests (FITs) with MPD provided the upper boundary.

Introduction

The SB field has a relatively high temperature gradient and abnormal-pressure regimes. Challenges in this HP/HT environment include a reduced kick tolerance, narrow drilling margin, higher drilling-fluid densities, high temperature (limitations in formation-evaluation equipment), wellbore ballooning, and availability of personnel experienced in HP/HT drilling.

Well SBD-2 had been considered undrillable because of its very narrow safe-drilling margin. The previous attempt to drill through the F and H reservoir sands, Well SBD-1, suffered an influx from the formation that exceeded kick tolerance and compromised the fracture gradient, resulting in total fluid losses. Well SBD-1 failed to reach total depth (TD) despite the use of an MPD system—200 m shy of the geologic target. Well SBD-2 was drilled only 50 m away from Well SBD-1. Given the close proximity, there were offset pressure data for planning Well SBD-2 down to a depth of X240 m, but beyond this depth it would be exploratory drilling. Given the uncertainties that would be encountered drilling past X240 m, the engineering team sought best practices and technologies that would provide the greatest chance of success drilling into such a tight margin at high temperature.

The 8½×9½-in. reservoir section would use an automated MPD system to mitigate drilling risk complemented by an FPWD tool in the drilling bottomhole assembly (BHA) to provide direct pressure measurements. The MPD sys-tem was used for early kick detection (EKD), FITs, dynamic flow checks, and constant-bottomhole-pressure (CBHP) control for a safe mud-weight window that was expected to be less than 0.9 lbm/gal. The high mud weight needed to drill this formation resulted in a high equivalent circulating density (ECD) throughout the section, requiring the MPD system to maintain a static condition between 0.2 and 0.4 lbm/gal. The FPWD tool would provide pressure data to establish the lower limit for the MPD fingerprint tests, and to serve as calibration points for the pore-pressure model. The objective in this 8½×9½-in. section was to maintain overbalance in the narrow window between pore pressure and fracture gradient. These tight drilling margins required use of an automated MPD system with software capable of predicting temperature effects and annular-pressure behavior during any well-control situation.