Abstract

Thousands of new wells are being drilled each year while thousands more are being repaired or abandoned around the world. Remedial and well abandonment work is becoming increasingly important for both E&P companies and energy service companies providers as the oil and gas industry continues to recognize the financial and environmental impact, while at the same time, authorities are tightening regulations.

Traditional abandonment and squeeze methods have not changed much over the past several decades which has resulted in little or no improvement on the successful repair and abandonment of wells. While improvements have been suggested and trialed, remedial work is viewed as a cost burden, and companies tend to avoid it rather than to address it, which often leads to problems occurring or reoccurring in the future.

However, in Western Canada one particular technique has been successfully developed. Although not a new technology, abrasive jetting has proven to be one successful component in well repair operations in many parts of Alberta. Abrasive jetting was primarily developed for wells presenting surface casing vent flow (SCVF) problems. According to the Alberta Energy Regulators (AER), approximately one in 20 oil and gas wells in Alberta experience gas migration to surface through one of the following issues: a cemented casing string(s) with either a micro-annulus between casing and cement, a channel within the cement sheath, or a channel between the cement and the borehole wall. To remediate these possible gas migration passages, the abrasive jetting technique is used first to radially cut the casing, the cement sheath, and the formation in the horizontal plane utilizing a high-pressure sand/liquid mixture. Cutting in this manner provides full radial exposure and increases the chances of intercepting the gas flow passage.The next step is to determine the formation feed rate. Once the feed rate is determined, the proper product can be selected along with the placement technique. Micro-fine cement with slow-rate pumping is often used in the squeeze process to seal off the channels.

This process is highly effective in terminating gas migration (GM) or SCVF and reducing remedial costs, saving E&P companies thousands of dollars in rig time and material costs, and adding significant value for the client.

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