Schlumberger

Case Study: Subsurface Assurance FEED Study Validates a Centralized CRI Project

Challenge: Identify, evaluate and design the cuttings reinjection (CRI) technology as centralized facility in an area with limited space and restricted permitting process for landfill disposal.

Solution: Implement Front End Engineering Design (FEED) to examine the basis of design, surface and subsurface technical conditions and implications to identify an environmentally feasible location for centralized CRI facility.

Result:

  • Validated suitable subsurface formation for CRI as well as waste containment for environmental compliance.
  • Assessed the subsurface formation capacity and waste domain to accommodate high volumes of waste.
  • Evaluated well design for CRI.
  • Determined the operational parameters and injection conditions for proper equipment design.
  • Outlined the high-level risks to the CRI project and mitigation options.

Using FEED study to evaluate CRI feasibility

An operator in the Oso field in Ecuador sought a suitable location to handle large volumes of slurry for
reinjection. An increase in the waste generated from drilling activities increases the risks associated
with environmental and social impacts. The objective for the customer was to identify and validates
a centralized CRI facility area that did not negatively affect the community or environment.

A Front End Engineering Design (FEED) study evaluates the subsurface and environmental feasibility
of CRI and identifies the optimal operational and injection parameters for environmentally safer,
efficient, and cost-effective CRI. A fully planar 3D hydraulic fracturing simulator modeled the fracture
propagation behavior. Applying these techniques to the validation of subsurface conditions made it
possible to identify containment and confinement formations and verify the fracture domain is far
from the near wells or any other geological hazards.

The FEED study also included the selection of surface equipment for the project. Evaluating surface
equipment considers the waste volume and streams involved in the process, including utilities and
footprint. A centralized facility requires additional considerations for logistics and sufficient onsite
temporary storage under high-volume scenarios. The surface equipment needs and sufficient space for
temporary onsite storage were identified along with a proposal for the necessary size of the facility.

Validating the centralized CRI facility concept

A complete set of injectivity tests are needed once the FEED study is completed, and prior to initiating
operations, to provide the first direct evaluation of injection pressure needed to conduct CRI operations.
The test provides a reference line for the in situ parameters of the disposal formation, the means to
calibrate the geomechanical model, and alignment of the hydraulic fracture simulations results.

Previously, a third-party vendor performed an injection test in the same area without considering all
subsurface parameters including the poroelasticity effect and the multiple fracturing complexities in
the injection formation. The vendor’s results indicated poor feasibility of CRI injection because of high
pressures and the inability to inject more than 2.5 bbl/min [0.40 m3/min].

FEED engineers in M-I SWACO proposed a new procedure taking into consideration the presence of
the high poroelasticity conditions in the formation as a results of the technical subsurface evaluation.
The new procedure included a correction in injection fluid properties to mitigate the effect of the
poroelasticity while performing the injection test.

M-I SWACO, a Schlumberger company, performed the formation injection tests designed to promote fracture propagation while mitigating the known effect of poroelasticity, which impacted injection pressure. Pressure analysis techniques were used to calculate the subsurface parameters for calibrating the geomechanical model previously constructed for the field and to verify the pressure conditions expected during operations. The assessments helped identify vertical fracture growth and a reduction of poroelasticity in the formation, allowing injection of up to 7.5 bbl/min [1.19 m3/min].

The new injection test results validated injectivity in the formation and demonstrated the importance of an adequate procedure and integrated subsurface assurance approach before the injection of the first slurry batch. Tests were completed without reaching the maximum allowable surface pressure—even at 7.5 bbl/min.


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