Lower Tertiary Wilcox Pressure Study

A significant new study, completed in  2010, which provides a comprehensive and authoritative picture of formation pressure distribution in the region, based on data from 149 wells.

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 was supplied by IHS in the form of the Gulf of Mexico Pressure Database, which included 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 were used to analyse the Lower Miocene, as well as study shale pressures throughout the stratigraphic column. Wells selected for the study included 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.

Deliverables:

• Maps and plots illustrating the overpressures across the area in the Deep Miocene and Lower Tertiary Wilcox intervals.
• Chapters exlaining evidence for lateral drainage in sub-salt reservoirs and implications for exploration in the region.
• Multi-Well Pressure - Depth plots for formation pressures.
• Analysis of 28 key wells in which full shale-based pore pressure prediction has been completed, as well as an exploration of the relationship between reservoir pressures and shale pressures.
• Lithostatic and fracture pressure models which can act as predictive algorithms for future well-planning.

Complete our Pressure Study Request Form to find out more about purchasing your own copy of the Lower Tertiary Wilcox Pressure Study.