choate technology

choate technology
Choate Technology Services Ltd 

Leading energy and environmental consultants






Waterflood and PWRI Induced Fractures

Water injection wells often operate above fracturing pressure. In deep high permeability reservoirs this is caused by injection temperatures significantly cooler than the hot formation resulting in thermo-elastic stress reduction around the wellbore. In low permeability reservoirs it is caused by build up of high pressure transients that exceed the poro-elastically changing in-situ stress.

CTS has developed a state of the art screening model TRIFRAC that simulates this process and can additionally predict (a) the effect of fines impairment due to injection of dirty water (PWRI) and (b) the eventual loss of vertical fracture containment as the fracture grows to a critical length.

TRIFRAC couples water injection into the formation with volume storage in the fracture so that hydraulic fracturing
of bounding shale intervals can also be considered.
Presently, CTS is devising a new type of PRWI model using a fractal approach that accounts for injectivity decline above fracturing conditions.


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Extended Reach Drilling Feasibility Studies

CTS has considerable worldwide experience in the design and feasibility assessment of challenging extended reach wells. All aspects are thoroughly investigated using state of the art software including wellpath design using geological visualization tools, extensive data gathering from offset well data and casing design using casing stress analysis tools.

Operational requirements are also assessed and defined including torque and drag analysis for both drilling and
running casing, required rig hoist capacity, wellbore hydraulics, pump sizing, liner specifications, hole cleaning and borehole stability. Additionally, CTS has developed in house the basis for a hard drillstring model HARDRILL for which potential applications are being sought.


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Borehole Stability and Sand Failure

CTS is advancing state of the art of borehole stability modeling by introducing new types of constitutive laws that offer far more accurate descriptions of rock failure than can be achieved with traditional elasto-plastic models.

For sand formations, CTS plans to test a combined clay and sand critical limit state model developed by Nottingham University. For more brittle formations, CTS is developing damage constitutive equations relating to fractal descriptions of rock failure. This is an ongoing research effort for which the company intends to apply for a SMART award.


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Drilling and Producing in Hydrate Formations

CTS has built up considerable experience in assessing the potential hazards that may be encountered when drilling through near seabed hydrate formations and subsequent problems that may also ensue in these formations during long term production of hot reservoir fluids from deeper zones.

To assist in assessing the seriousness of this geohazard, CTS has developed an analytical model HYDISS that simulates the progress of a hydrate dissociation front away from a wellbore in response to wellbore fluid temperatures exceeding the hydrate dissociation pressure temperature relation.


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