This following case study details the methodology followed and challenges encountered while drilling in the Shakal Block of North Iraq. A narrow drilling window and geologically-associated problems in the first well, Shakal-1, were enough to demonstrate that non-conventional drilling techniques are needed to develop Shakal field potential. In case of Shakal-2 and Shakal-3 exploration wells, the 12-¼" and 8-½" hole sections applied Managed Pressure Drilling (MPD) technique and Microflux® control system technology to reach planned objectives and reduced a combined 15 days of drilling time, equating to associated cost savings of US$1.8MM.
The primary objective of drilling with these techniques in the Shakal field was to maintain the Equivalent Circulating Density (ECD) within the operative window and keep the downhole circulating pressure close to formation pore pressure in order to minimize nonproductive time, optimize drilling performance and minimize formation impairment.
In addition to the drilling objectives, MPD help was needed in order to safely facilitate trips to surface derived from normal scheduled operations as well as unprogrammed operations caused by tool failures or drilling problems; in some fields like Shakal, pulling out of hole can be equal or more difficult than the actual drilling operation.
All planned operating windows have some degree of uncertainty. In the cases of Shakal-2 and Shakal-3, Microflux control system technology detected early signs of influx and fluid loss when there was a deviation from the anticipated drilling window.
The flexibility of MPD technique during trips with Stripping Method showed high benefits on these holes sections along with accurate monitoring of well parameters for early detection of influx and losses.
The use of MPD contributed to significant time, cost savings and safety increment for the Shakal-2 and Shakal-3 in the 12-¼" & 8-½" hole sections.