Lower Completion Optimization Using Ultra Deep Resistivity Tool Improves Reservoir Management and Lower Water Production in Giant Carbonate Reservoirs in the Middle East
Authors: Barragan E. , Holmquist A. , Thakur P. , Alshalabi A. A. , Sidek M. Muhamad 
Published: October 2023

Field Development in mature oil reservoirs is a challenging task in the oil industry. This is especially important where aquifers are present, water mobility is higher than oil and water management is crucial to maintain production considering the associated operational costs.

Drilling horizontal wells is a method of improved oil recovery where maximum reservoir contact is attained through the horizontal section along the target zone as opposed to vertical or deviated wells where a limited part of the reservoir is exposed.

In the case presented for oil production carbonate reservoirs, the method of improved recovery is through peripheral water injection initially and nowadays moving to line pattern, using infill drilling. As a result, water production is a challenge with reverse coning being the main source of unwanted water coming from the upper layers within the same reservoir.

The study comprises the analysis of long horizontal wells in carbonate reservoir B, using the ultra-deep resistivity tools utilization for lower completion optimization while the rig is on site. In addition to the water encroachment problems, we must add the presence of faults that may act as high permeability streaks in some areas, increasing the water production coming from the flanks and neighbor injectors.

Logging While Drilling is currently utilized as the standard method of measuring reservoir characteristics in the A Field under study. The limitation comes from the depth of investigation, with standard tools it is only possible to determine the water saturation in the near wellbore vicinity. Ultra-deep resistivity tools help to overcome this constraint, allowing the measurement of the resistivity in 1D above and below the wellbore while drilling. Therefore, resistivity can be measured in tens of feet, even more than one hundred feet in some cases. Identifying the conductive zones allows the lower completion optimization, to avoid future unwanted fluids and potentially improve the recovery in the long term.

Lower Completion is required for reservoir management, to achieve accessibility and cater for future reservoir conditions (i.e., water shut off, stimulation, among others).

The paper presented shows the planning, logging results, and lower completion selection process and its optimization in real-time. This is done right after the interpretation of the logs is in place, with the rig on site. The service utilized in the first well is presented in the current paper.

Results of the first oil producer well are presented, showing the well is producing oil with almost zero water cut. This is in contrast with the nearby wells and contrary to the expected higher water saturation expected in the region. Saving millions of dollars in future interventions while improving the reservoir management process.

Ultra-Deep Resistivity tools allow the Geosteering Team to identify the pay zone (high resistivity) above and below the wellbore. The depth of investigation is in the order of tens of feet. Proper identification of the water saturation in the vicinity of the well provides a quick look interpretation of the water saturation. As a result, the lower completion is optimized (i.e., high water zones are isolated).