Role of Formation Pressure and Sonic Measurements While Drilling in Pre-Drill Well Design Validation and Syn-Drill Well Design Optimization - Case Studies from Deepwater, India
- Vikas Agrawal (Schlumberger Asia Services Ltd) | Rajesh Kumar Singh (Schlumberger Asia Services Ltd) | Juli Singh (Schlumberger) | M.I. Shaikh (Oil and Natural Gas Corporation Ltd.) | Firoze Dotiwala (Oil and Natural Gas Corporation Ltd.)
- Document ID
- Society of Petroleum Engineers
- SPE Middle East Oil and Gas Show and Conference, 25-28 September, Manama, Bahrain
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 5.1.6 Near-Well and Vertical Seismic Profiles, 1.12.2 Logging While Drilling, 1.6 Drilling Operations
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Deepwater exploration is a challenging and cost-intensive endeavor. Optimal well design is critical to both cost control and successful execution of the drilling plan in this difficult arena. Generally, offset well data is very sparse for deepwater wells; therefore, it is critical to have real-time measurements while drilling to enable comparison with the pre-drill design model, allowing deviations from the plan to be noted and acted upon. Such quick analyses while drilling allow for midcourse corrections in the well design that not only help to drill safely at minimal cost, but also to maximize exploration returns in the form of reserve accretion.
The case studies discussed in this paper are examples where formation pressure-while-drilling (FPWD) and sonic-while-drilling technologies have been leveraged to enable while-drilling validation of pre-drill design and midcourse corrections in the well design. Proactive decisions on well design modification, including mud weight program, were taken which resulted in achieving maximum drilling efficiency and optimal quality of data acquisition at minimum cost. The use of FPWD and sonic while drilling technologies resulted in major cost savings in addition to obtaining vital geological and petrophysical data in the formation free of invasion-induced damage, against both argillaceous and arenaceous intervals encountered while drilling the well. This allowed for integrated analysis with already available VSP data and other data while drilling and resulted in deciding upon optimal section TD in at least one instance.
Pore pressure and fracture gradient prediction while drilling helps define the safe mud weight window in real time and allows maintaining wellbore stability as the well drilling progresses. In exploration drilling, real-time definition of the safe mud weight window together with equivalent circulating density (ECD) management are the cornerstones of any endeavor aimed at delivering a stable hole and ensuring their assessment at optimal cost. The advent of logging-while-drilling (LWD) technology has made it possible to address above mentioned critical requirements by ensuring real-time availability of measurements such as basic petrophysical logs, shear and compressional slowness, formation pressure and annular pressure while drilling.
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