For many years, coring operations suffered from frequent jamming due to abrupt changes in lithology and rock properties. Core jamming leads to potential core damage, excessive number of trips, longer operation time and thus higher cost. Frequent and abrupt lithology and rock property changes are natural occurring phenomena. To mitigate the implications of core jamming, a robust coring technology platform has been deployed, which allows alternating between coring, pressure coring and drilling without pulling out the drillstring. The applied wireline-retrievable coring technology offers an efficient and cost effective way to trip-out large diameter core, thus achieving high recoveries of high quality cores. It also allows the Operator to almost decide real-time to drill ahead or to retrieve additional cores without performing additional trips. The coring/pressure-coring/drilling assembly is designed in such a way that it is efficient to switch from coring to pressure-coring or to drilling modes and vice versa, without tripping the drill pipes. By eliminating trips, this technology is extremely cost effective for multiple coring targets, especially when incorporating inter-drilling sections. The wireline-retrievable coring technology was also successfully applied to obtain pressure core, deploying breakthrough technology for the first time in the Middle East that retains the hydrocarbon content in its native state, with no lost gas, until core retrieval and evaluation on surface. This paper describes a case history of the first deployment of the wireline-retrievable coring/pressure-coring in the UAE and the Middle East, while saving significant rig time compared to conventional coring.

A recent exploration well in the UAE was drilled through a gas zone in extremely tight carbonate rock. The evaluation success of this interval hinged on the production of gas to surface to confirm the presence of hydrocarbon. After drilling the well and running the completion the rig was demobilized and the testing work was carried out using rig-less techniques. An abrasive jetting stimulation technique was attempted but was unsuccessful. The zone was finally tested using wireline conveyed perforating guns followed by wireline conveyed propellant stimulation equipment. After the first perforating run with a premium deep penetration gun system gas started to accumulate at surface confirming that a connection had been made to the reservoir. This accumulation in the pipe was bled off occasionally and continued to build through the remaining perforation runs. After perforating was completed each interval was treated with a propellant assembly which increased the rate of gas build-up significantly indicating value of the propellant treatment. The entire job progression was recorded with a surface pressure recording device. This paper will review the obstacles encountered to test this tight unconventional reservoir, the planning for this job including the risk assessment and modeling for the propellant runs, along with the status of the perforating and propellant equipment as it was returned to surface. The techniques used to confirm this reservoir contained gas that could be produced to surface have applications in many unconventional reservoir exploration wells and for many operators in the region.