Deep-Water Gulf of Mexico

How much does it cost to drill a dry hole in the Wilcox?

Although a number of high-profile discoveries have been made to date in the Wilcox play, e.g. Tiber, Cascade & Jack, costs of $150-$250 million per well have also generated some expensive dry holes, in search of hydrocarbons trapped beneath salt, e.g. Sardinia & Hadrian. Many of these wells have experienced high pressures, some with narrow drilling margins and it is believed that understanding pressures will assist greatly in future exploration and development of this important play.

Dataset
Data provision for the study is supplied by IHS in the form of the Gulf of Mexico Pressure Database, which includes direct fluid pressure data (RFT and ‘kicks’), fracture pressure data (FIT/LOT and LC events) and mud pressure data.

After extensive data-mining of wells in AC, AT, GB, GC, KC & WR a final list of 149 wells has been identified combining data quality with geospatial distribution.
49 of these have TDs’ that penetrate the Wilcox reservoir.

The other wells will be used to analyse the Lower Miocene, as well as study shale pressures throughout the stratigraphic column. Wells selected for the study include sub-salt and those beyond the salt canopy.

Approach

• Re-interpretation, standardisation and QC of formation pressure using the IHS Pressure Database and related data i.e. Biostratigraphy, Wireline Data, Directional Surveys and Temperature (BHT & Wireline derived).
• Analysis of pore fluid and fracture pressure data for all wells including creation of single- and multi-Well pressure-depth plots using Ikon Science’s RokDoc-PressureView software.
• Mapping of the distribution of formation overpressures at all main reservoir horizons using ArcView GIS software.
• Determination of fracture and overburden pressures stratigraphically, regionally and in areas both beneath and outside the salt canopy.
• Focus on trap integrity/seal breaching, hydrodynamic traps, lateral transfer/”centroid” development, pressure regressions, reservoir compartmentalization and shale pressures.

Benefits of the study include:

• Reduced drilling risk with associated savings to time and cost.
• A coupled pressure-geological model to aid calibration of velocity-based pressure prediction in un-drilled areas.
• Potential to increase reserves close to existing facilities plus identify new exploration potential.
• Improved understanding of the regional pressure regime and its part in controlling aspects of the petroleum system, including trap integrity and regional/field-scale fluid flow.
• More accurate placement of appraisal wells.