Schlumberger

Case Study: 850% Increase in Injection Rate While Satisfying EPA and UIC Requirements for Colorado Injection Wells

Wireline logging tools used to efficiently assess injection zones in challenging salt formation

Challenge:

  • Gain regulatory approval to construct a water treatment plant by verifying the performance of injection wells.
  • Identify the most efficient injection zones in terms of formation characteristics and water quality.
  • Successfully drill 7,000-ft- [2,100-m-] deep injection wells in challenging salt formation.

Solution: Run the Platform Express integrated wireline logging tool and CHDT cased hole dynamics tester, guided by knowledge of local conditions, to effectively verify injection performance and use this information to drill and complete injection wells.

Result: Identified and developed two new injection zones with the new methodology, ultimately increasing the injection rate by 850% while increasing system reliability, reducing long-term costs, and ensuring permitting approval and regulation compliance.

Confirming injection capacity in a challenging salt formation

The City of Sterling, Colorado, was planning to build a water treatment plant. To advance its existing water supply system, the city selected a water-treatment process with a disposal stream. A subcontractor designed two 7,000-ft- [2,100-m-] deep Class I Underground Injection Control (UIC) wells with eight injection zones with a targeted injection rate of 350 galUS/min [79.5 m3/h]. To confirm the injection capacity, the city selected Schlumberger to drill and complete the injection wells.

The target injection zones are in the presence of salt formations, presenting significant drilling challenges. Compounding the salt challenge was the depth of the two injection wells and risk of possible loss of well control, lost circulation, and stuck pipe.

Reducing long-term costs while remaining compliant

To overcome these issues while ensuring minimal drilling time and costs, Schlumberger Water Services and M-I SWACO, a Schlumberger company, developed a customized drilling program designed to successfully target the injection zones despite the local salt formations. The Platform Express integrated wireline logging tool was used to perform openhole logging, and these results helped determine that the permeability of the target injection zones would provide an injection rate of 200 galUS/min [45.4 m3/h]—well below the target requirement of 350 galUS/min.

Obtaining approval and meeting water treatment objectives

Based on knowledge of the local formations, Schlumberger Water Services recommended and obtained approval to use the CHDT cased hole dynamics tester to evaluate potential injection zones. Through effective formation evaluation techniques and completion workflows, Schlumberger Water Services confirmed that two formations not previously considered in the plan were viable additional injection zones. Schlumberger Water Services performed and evaluated injection tests, confirming that these new injection zones could receive injection rates at 2,000 galUS/min, which will reduce the long-term costs by lessening pumping requirements. Also, all EPA and UIC regulations were met by

  • verifying cement integrity for zonal isolation using a cement bond log
  • confirming that more than 10,000 mg/L total dissolved solids was present by using the CHDT tester to collect water samples and verifying the results by swabbing
  • maximizing the injection rate through an effectively designed program of perforating and acidizing
  • confirming the injection rate through step-rate testing and determining the maximum-allowable breakdown pressure.

Further, each injection well was drilled in a single run and within time and cost parameters.


Download: 850% Increase in Injection Rate While Satisfying EPA and UIC Requirements for Colorado Injection Wells (0.27 MB PDF)

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Openhole Logging Helped Determine Permeability

Installation of the CHDT tool into one of the Sterling injection wells
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