Customer’s problem

An operator of a shallow (~2,100 ft) Coal Bed Methane well in the San Juan Basin used a sand hydro-jet tool to create holes in their 7-inch casing rather than perforating the casing with conventional perforating guns. After hydro-jetting the holes, the operator wanted to gain more information on the sand hydro jetted holes, including the depth control precision, the size of the holes, the effective penetration, and the elliptical nature of the holes. The operator decided a downhole camera with the ability to view to the side would be the best tool to evaluate the conditions.

Expro’s solution

Expro’s ViewMax camera system, which provides both downview and sideview cameras in the same tool, was mobilized and run in the well. The flexibility of the camera system to operate on conventional electric line allowed Expro to mobilize a man and equipment with short notice to location saving valuable rig time.

Results

The good points:  The camera inspection revealed that in fact there were 3 holes sand blasted in a single plane, the holes were very spherical in nature and placed within 6 inches or less where thought to be.
Not expected was the bevelled nature of the holes and the ability to see partially into the holes.  The camera showed some holes had pieces of coal and/or sand grains blocking them along with fluid movement into the wellbore. In one instance the holes looked like an old key hole, in this instance it was thought that the sand jet had not penetrated the casing and the tool was subsequently moved slightly up-hole, thus creating the key hole design.

One important fact that was unknown was the amount of time or the sand concentration required to cut effective holes in the casing.  Tests were conducted varying time and concentration.  It appeared that efficiency could be gained by cutting back both the time and sand concentration while maintaining effective communication with the reservoir.  This data provided the basis to reduce jetting time and sand concentration needed to cut the perforations in subsequent jobs, saving valuable time and investment.

Technologies used

The advent of a downhole camera that can look both down and to the side and rotate 360degrees is allowing operators to see much more than was possible with only the conventional downview camera.  No other tool could lend such certainty to the wellbore conditions and allow operators in these types of environments to make the best decisions to deal with a problem as the ViewMax camera.