Traditionally, brown field developments have often required the plug back and sidetrack of existing drain holes, to target any nearby opportunities. With advances in drilling technology, there is a general preference to drill small diameter wells due to the comparative cost advantage.

In the recent times, this preference has led some wireline service companies to start to offer open hole formation evaluation services with slim tools having a diameter in the 2" to 2½" range. At present, most of the traditional petrophysical measurements can be acquired utilizing slim tools. In addition, several "specialized" measurements, such as cross dipole sonic, formation pressure testing, and resistivity imaging can also be acquired. The use of battery and memory technologies has allowed these tools to be deployed using a broader range of conveyance techniques allowing for reduced risk in the entry of slim wells.

The provision of slim hole logging services has created an opportunity in the industry to leverage these tools for the economic development of brown fields. Therefore, short horizontal sidetracks and well re-entry’s to test deeper horizons can be drilled and logged successfully. Saudi Aramco has been able to leverage these tools in its continued development of the giant Ghawar field. Some of the development projects are listed below:

  • Some horizontal sidetracks with 3⅞" hole sizes have been drilled under higher doglegs than was previously possible, and logged successfully.

  • It is now possible to run well completions in newly drilled wells that have a well control problem. A provision is made to subsequently log these wells with slim wireline logging tools.

  • It is now possible to run a complete suite of wireline logs across some old wells that were previously completed without a full formation evaluation logging suite.

  • Slim hole formation resistivity imaging services are now being provided, to aid in the identification of borehole breakout and fracture features that might affect the well’s productivity.

  • Slim hole formation pressure testing has been acquired in slim wells to generate a pressure gradient, determine oil mobility, and define oil-water contacts.

Several case studies will be used in this paper to demonstrate how Saudi Aramco has leveraged these slim wireline tools to realize some development opportunities. Also, examples will be used to show that these slim tools do not compromise the quality of log data acquisition.

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