Bagpuss contains degraded heavy oil, North Sea Energy says

North Sea Energy (NSE) has reported that the initial findings from the Bagpuss well in the UK sector of the North Sea show the prospect contains degraded heavy oil. 

The well, located in Licence P. 1943, was spud in July 2016 with Diamond Offshore’s Ocean Valiant semi-sub offshore drilling rig.

The license was previously operated by Premier Oil that abandoned it at the end of September, which was followed by an exit by another partner, Maersk Oil, earlier in November. Premier sold its stake in Bagpuss to Reach Halibut, an oil and gas company incorporated in the UK in July 2016. NSE is a partner in the license with 15 percent interest.

NSE said on Friday that a detailed geochemical study has been carried out by Applied Petroleum Technology (APT) on a series of wet unwashed drill cuttings, drilling mud samples, and smears of oil recovered from several pieces of downhole testing equipment, all recovered from the Bagpuss well drilled in the Inner Moray Firth area of the UK North Sea.

The main conclusions arising from this study are that the oil discovered in the well is degraded heavy oil, the company said.

Further, the company stated that the estimated API oil range from the well was 19°-11° API based on the “dead oil” from the cuttings and oil smears. The analysis indicated an overall oil quality of API of 12.5° and viscosity of 850 Cpt +- 150. Importantly, however, these values are estimates based on heavy oil field analogs as there was insufficient oil recovered to get direct measurements of API and viscosity.

NSE explained that the oil sampling program conducted by the Bagpuss operator, Premier Oil, did not result in a proper oil sample due to a number of factors. Oil sampling was attempted with a Saturn tool and observed in the grill of the Saturn probe as well as inside the pumps and some of this oily material was retrieved for analysis.

A sample of water, that proved to be formation water, was collected from one of the Saturn tool stations believed to be in the oil leg. It was subsequently suggested that one of the reasons that a proper oil sample wasn’t recovered was due to a reaction with between the oil and the water-based mud forming an emulsion.

During the sampling program, the XLD probe used was also plugged with drilling mud and there were problems with the Modular Formation Dynamics Tester sampling tool.

Oil from the well appeared to show ‘live’ oil and to be less viscous than the cuttings that were exposed to the drilling mud. APT speculated that “this may well be due to dissolved gas at the point in time when it came out of the hole. The ambient air temperature or tool temperature as it came out of the hole at the time may also have impacted the viscosity.”

NSE still sees potential in Bagpuss

J. Marcus Marsh, NSE’s Senior Reservoir Engineer, said: “The results given in the study are clearly based on ‘dead’ oil and thus present a worst case.

“However, we do know that the oil, when first observed, seemed rather livelier than dead. Unfortunately, with no worthwhile samples, we cannot tell what the properties are at reservoir conditions, but they can be expected to be better than those given in the report.

“So to sum up, the well proved up a significant oil column and thereby volume in place. Frustratingly, it didn’t give enough data to determine flow properties, although the porosity is good and the fluid properties are likely to be better than those stated. To this extent, the results are still encouraging. NSE still sees potential for further appraisal in the prospect.”