Deep Transient Testing Offshore Africa | SLB

Operator confirms well deliverability, reduces CO2e by 96%

Africa, Offshore

An operator evaluating an exploration well in offshore Africa partnered with SLB for comprehensive reservoir evaluation services conveyed on wireline. By using the Ora™ intelligent wireline formation testing platform instead of a DST, the operator confirmed production deliverability estimates of more than 10,000 bbl/d of oil while reducing GHG by 5,426 metric tons of carbon dioxide equivalent (CO2e).

The operator wanted to evaluate its exploration wells as accurately and effectively as possible to reach first oil with minimal appraisal time. SLB proposed the Ora platform for deep transient testing (DTT) on wireline, which would quickly determine hydrocarbon in place and zonal deliverability while reducing energy consumption and carbon footprint. But first, the operator needed to obtain realistic knowledge of the geological reservoir elements and their subsurface geometries to simulate the expected deep transient response for different scenarios.

SLB acquired well, density, neutron, and resistivity logs during drilling—followed by two logging runs to capture critical reservoir characterization data. Gamma ray, density, neutron, and resistivity measurements identified oil in the target sand, but no further differentiation within the target. However, sedimentary geometry measurements from Quanta Geo™ service revealed detailed zones of massive sand channel fill, laminated sand, cross beds, and several occurrences of local sediment slumping. These insights were crucial for evaluating the dynamic Ora platform DTT measurement.

For DTT, SLB ran the Ora platform in cased hole within a perforation interval of 1.5 m. SLB conducted a multirate flow test with maximum flow rates of 90 cm3/s and 49 bbl/d while simultaneously circulating drilling fluid from surface. Wellbore dynamics modeling enhanced operational safety by maximizing overbalance and minimizing dissolved gas in the annulus. Flowline decompression was used to measure both bubblepoint and fluid compressibility. Downhole fluid analysis data were used to fully tune the equation of state. Transient pressure analysis showed infinite-acting radial flow, with deep reservoir response approaching 200 m away from the wellbore. The dynamic response was placed into the static model for precise interpretation and history matching. Interpretation of the permeability thickness and total skin provided the inflow performance relationship for producibility of the reservoir at the sand face.

This integrated data enabled the operator to estimate a total well deliverability of more than 10,000 bbl/d. Compared with a conventional DST, the Ora platform DTT service reduced GHG emissions by 96%5,426 metric tons of CO2e—by eliminating flaring. Based on these intelligent wellbore insights, the operator expects to start production from the well within 6 months through a fast-track tie-in to the nearby FPSO. Using the same unique approach, the operator plans to evaluate future exploration wells in Africa.

 Integrated workflows enabling a fully calibrated reservoir model to confirm well deliverability.
The Ora intelligent wireline formation testing platform integrates smart hardware with digital capabilities to improve reservoir evaluation.