Kuwait Oil Company (KOC) deployed CMR-MagniPHI™ high-definition NMR service and Ora™ intelligent wireline formation testing platform to accurately characterize a depleted reservoir. An industry first, the Ora platform enabled openhole sampling in this deep, challenging reservoir with a 6-in borehole. Combined, the technologies helped adjust completion and stimulation design faster than conventional methods—saving significant time and costs.

The objective

The Kuwait North Gas Field includes Jurassic tight carbonate reservoirs with typical depths ranging from 14,000- to 18,000-ft MD, near-critical gas, and volatile oil fluids. These reservoirs have complex reservoir quality, fluid (high H2S content), and rock properties and pose both upstream and downstream production challenges. The reservoirs have been in production since 2008 with approximately 250 wells drilled to date. All wells are naturally flowing but were starting to suffer from liquid loading due to depletion and high backpressure from the surface production facility.

KOC wanted to more accurately characterize the reservoir, but it proved to be challenging due to uncertain conventional log measurements and deep oil-based mud (OBM) filtrate invasion. Due to the reservoir properties and operational challenges, openhole formation pressure testing and fluid sampling had been cancelled in most of the wells by the KOC drilling team mainly due to anticipated operational risk of differential tool sticking from the high depletion and differential pressure across the openhole reservoir section. This led to a lack of proper reservoir fluid characterization and high uncertainties (estimated pay zones, flow assurance, and stimulation costs and outcomes).

The solution

KOC needed crucial information to design effective stimulation treatments for improved production. To obtain this, SLB deployed two key technologies. The CMR-MagniPHI high-definition NMR service was run to detect the free oil, free water, and OBM filtrate invasion volume by using continuous T₁ and T₂ mapping. This high-definition NMR technology unlocks the T₁ dimension and enables unprecedented determination of shale porosity and reservoir fluid types and volumes for movable and nonmovable oil; high-viscosity hydrocarbon; and free, capillary-bound, and clay-bound water.

The Ora intelligent wireline formation testing platform enabled openhole sampling and analysis in this challenging depleted reservoir. Using its flow manager, the Ora platform covers a wider range of flow rates (0.1 cm³/s to 200 cm³/s) than conventional formation testing technologies (2 cm³/s to 30 cm³/s). In addition, it's in situ fluid scanner provides high-accuracy GOR, asphaltene content, onset pressure, formation volume factor, oil and gas compressibility, real-time gradients for lateral and vertical connectivity determination, gas/oil contact, and advanced contamination analysis. And its focused radial probe has both a large surface flow area and a dual flowline, making it ideal for both low-mobility and -permeability formations and sampling in miscible fluids.

The results

The Ora platform successfully enabled openhole sampling in this deep, challenging depleted reservoir with a 6-in borehole. The platform revealed the true reservoir content of formation water in just 2 h, whereas conventional formation testers would have taken 10 to 20 h. The collected water sample also matched the fluids computation from the CMR-MagniPHI service.

These technologies helped KOC improve reservoir fluid characterization before the completion phase, which was crucial information for the subsequent perforation design and testing plans. Completion and stimulation plans were then adjusted based on the sampling results. And the collected sample resulted in urgent modification of the completion and perforation plans in this well—saving significant time and costs. In the future, these technologies will enable frequent collection of openhole fluid samples to support robust dynamic modeling and predictive capabilities.