Undergraduate Honors Theses

Thesis Defended

Spring 2019

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Geological Sciences

First Advisor

Shemin Ge

Second Advisor

Rebekah Simon

Third Advisor

Megan Brown

Abstract

Oil and gas wells in Colorado had a circular spacing regulation that required wells to be spaced 745 ft (227 m) in diameter apart. Some oil and gas wells in the Piceance Basin experience hydraulic communication, which is when the hydraulic fracturing of one well damages the production of a neighboring well. During hydraulic communication, formation water enters the producing borehole at the front of the pressure wave and must be removed before the well is brought back into production. Several wells that have experienced communication have come back on line, but months later, have not recovered their original production rates. It is known that when communication occurs in this scenario there is an increase in the casing pressure of the pumping well of 400 psi (280 meters of head). During hydraulic communication, the bedrock formation experiences long term damage. To test this hypothesis, MODFLOW is utilized to model a generalized two-well system in which a producing well and hydraulic fracturing well are approximately one mile (1,610 m) apart. Modeling is conducted to test how geologic heterogeneity in aquifer conductivity and specific storage, and engineering parameters including well spacing and hydraulic fracturing injection rates affect the change in hydraulic head between the injection well and the pumping well. By changing these parameters in a sensitivity analysis, it is possible to determine which have the greatest effect on hydraulic communication.

Overall, the systems with lower hydraulic conductivity, higher specific storage, and increased well spacing have a decreased probability of well-to-well communication in the Piceance Basin. Hydraulic communication in the Basin is due to geologic heterogeneity of the area. However, for impacted wells, hydraulic communication can cause both unexpected short-term expenses and permanent economic loss. It is therefore critical to understand the appropriate geological parameters for communication minimization, despite a fairly limited number of occurrences thus far. Additionally, a better understanding of hydraulic communication between wells will provide new knowledge for Colorado regulators to reevaluate their current spacing regulations.

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