| 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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| 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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| 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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| 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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