JIP on Measuring Pore Pressure in Shale, MESPOSH

Objective

The overall objective of MESPOSH is to develop a reliable and economical system for direct pore pressure measurement in shale. The project will be executed in two phases as follows:

1. Develop measurement systems, ideally comparing two different methods.
2. Verify the systems by a field trial.

Motivation

Shale is the predominant lithology found in petroleum basins: most of the drilling time and seismic travel time takes place in shale. Yet it remains mechanically the least understood rock type because of lack of reliable pressure measurements.  Pore pressure, together with total stress, defines the effective stress, which controls the mechanical behaviour of rocks in terms of strength and stiffness.  Direct pressure measurement in shale adds value to all aspects of the petroleum industry including

• Seal risking: shale is the most common seal lithology and determination of minimum effective stress is essential in oil reserve estimation.
• Fluid flow in the basin.
• HSE and cost risk reduction in drilling: Shales are commonly overpressured (pressure higher than hydrostatic).  Pressure measurements translate into more effective and safer well design and drill rig selection.
• Reliable interpretation of seismic data and for assessment of the interaction between the reservoir and the surroundings during the lifetime of the field.

Despite its importance, no reports of direct measurement of pore pressure in shale are found in the petroleum industry - it remains one of the last outstanding items on the list of primary mechanical parameters for optimal hole stability assessment, seismic interpretation and fluid flow modelling. It is time to address this issue.

Application

Several applications are foreseen for MESPOSH

• A primary application of direct pore pressure measurement in shale is to calibrate the existing indirect methods of pressure prediction.
• Measurement in exploration and appraisal wells to speed up the learning curve in new areas and thereby create added value to drilling and exploration risking.

• An additional application is shale zones near or within reservoirs with severe depletion, for instance HPHT fields. Production related pore pressure changes in such zones are important for drilling in depleted reservoir and also for new technologies such as 4D surveillance in combination with geomechanical modeling.
• Tight reservoir.