Abstract

Bakken well activity and oil production has increased dramatically in recent years, largely because of technological advancements in drilling, completion, and hydraulic fracturing. For one North Dakota operator experiencing downhole calcium carbonate scaling in the pump and production tubing, an innovative inhibition program has been implemented and shown to reduce well scaling frequency. The new scale inhibition program utilizes a solid proppant-based additive from which the scale inhibitor gradually desorbs. With expansion of the development into new fields which exhibit lower scaling risk, the scale inhibition program was then limited to the higher scaling risk fields, reducing cost and simplifying operations.

Bakken wells are completed to vertical depths of approximately 10,000 feet with horizontal laterals up to 10,000 feet and produced via multi-zone completions. The operator initially applied high concentrations of liquid scale inhibitor as an additive to fracturing fluid; nevertheless scaling remained a recurring problem. A postmortem of the failed wells was conducted to eliminate failures not directly attributable to calcium carbonate scale and to identify the factors affecting the scale deposition. The postmortem considered the method of hydraulic fracturing, pump intake pressure, scale inhibitor residual, calcium carbonate scaling index, geographic failure concentration, production time to failure, and cumulative water production to failure. Results of this study are detailed in paper SPE 140977 (Cenegy et al. 2011).

This paper continues the study and describes the subsequent scale management program initiated. It details the technology implemented and results in effecting downhole failures due primarily to scale. The paper additionally discusses the solid scale inhibitor technology selection, the inhibitor placement process and the steps taken to further optimize and manage costs of the field-wide Bakken scale inhibition program.

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