How North Sea operators saved 414 rig days

Overview 

In the Norwegian sector of the North Sea, environmental regulations require cementing every permeable zone before abandoning a well. Because cement must go all the way to the formation, operators used to mill out casing and remove tons of swarf before spotting the cement. In addition to being expensive and time-consuming, this operation prevented re-entry into the wellbore. The HydraWash system can perforate, wash, and cement wells in a single trip, and greatly increases displacement efficiency by placing cement in a much more controlled manner. This method allows operators to re-enter the well to verify cement integrity. It also saves time by eliminating the need for milling and removal of swarf. The HydraWash system complies with all Norwegian regulations, which are among the most stringent in the world. The system helped operators in the North Sea save 414 rigs days while plugging and abandoning 67 offshore wells.

Challenge 

Norwegian regulations call for isolating all permeable zones before plugging and abandoning wells. Cement must extend a minimum of 50 meters above any source of inflow. Hydrocarbon-bearing formations require two such barriers. Traditionally, companies complied with this regulation by milling out 50-meter sections of casing, often in multiple runs. Then they had to remove swarf. Finally, they had to use an under-reamer to create a clean section in the formation before cementing. Each 50-meter section took 10.5 days and generated four tons of metal swarf. The sharp swarf often damaged expensive BOPs, which had to be inspected and refurbished after each job at great expense. After completion, this traditional method also prevented operators from re-entering the wellbore if a problem developed or if future technologies made it economically worthwhile to recover reserves left in the ground.

Solution

Setting one 50-meter isolation plug using the traditional method used to take an operator 10.5 days and four trips for milling, clean out, under-reaming and cementing. Using the HydraWash system, they can now achieve comparable results in less than three days and one run. But the savings are even more dramatic. The HydraWash system can handle two zones on the same run, so treating two sections takes just 3.5 days.

Result

One major operator in the North Sea began using the HydraWash system in 2010. Since then, the system has had a 99.3% success rate. The system was originally conceived as a hydraulic perforating system, but has evolved to include explosive perforating guns, washing tools, a cement stinger, and cement assurance tools. Since its introduction, the tool has also evolved from a triple- to a double- to a single-trip system. With more than 3000 wells in the Norwegian sector of the North Sea that need plugging and abandonment, savings due to HydraWash technology could total billions of dollars. One major operator in the area estimates that HydraWash technology has already saved the company more than a quarter of a billion dollars while setting just 55 barriers.