Abstract

In a heterogeneous and fractured carbonate hard rock with UCS more than 15K psi, drilling a highly deviated well is a challenging process that would require real time monitoring, using best in class MWD and LWD technology. A client in South Oman is in a development phase of drilling 1000m lateral wells to maximize the exposure for optimum oil production.

The carbonate formation is characterized as heterogeneous vuggy dolomites with a network of regional fractures acting as the secondary source of porosity. The thin reservoir is isolated by thick layer or Anhydrites above and Shale formation below & managing geological uncertainties in real time is going to be the differentiator between success and failure. A combination of hybrid RSS to manage aggressive steering requirements along with distance to boundary imaging LWD tool to identify the bed boundaries & keep the well on course along with an azimuthal resistivity ultra-high imaging for reservoir characterization were deployed to overcome these challenges.

The proposed solution was put into challenge on well X for drilling 5.87in lateral section and 1000 m lateral was successfully drilled. Hybrid RSS with aggressive bend setting helped in geo-steering the well and managed to achieve directional objectives to chase the geological uncertainties. After confirming the formation dip the well was steered 6to 7ft from the bottom conductive layer with the help of distance to boundary resistivity imaging tool. Real-Time High-Definitionazimuthalresistivity images helped in petrophysical interpretation and formation evaluation. Later, better density memory imaging data helped in evaluation of full borehole structural features and detailed fracture characterization. Hybrid rotary steerable systems along with best in class LWD tools provide purpose to fit solution to drill and geo-steered well in the optimum place. Success of this combination has eliminated the risk of exiting the reservoir leading to costly sidetrack scenario. At the same time, it has also helped the client to optimize production by geo-steering the well in the high porosity sweet spot and by Identifying regional fractures.

Developing deep, hard and heterogeneous carbonate reservoirs is a complex and challenging affair and a conventional approach to overcome these challenges is not always producing the best results. A novel approach with the help of advanced rotary steerable and logging while drilling tools helped client in developing the field by minimizing the risks and maximizing the best reservoir exposure characterized, as the well are drilled.

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