With the increase in slimhole wellbores ranging from 93.2 mm to 123.8 mm being drilled, specifically within Russia, comes the need for logging while drilling (LWD) technology to provide real-time formation evaluation data to better analyze the reservoir and enable improved well placement. The authors describe the development of a 79.4 mm propagation wave resistivity system designed to facilitate the low cost drilling of small, shallow boreholes using coiled tubing drilling (CTD) technology, from which an 88.9 mm system was developed to address the Russian slimhole market. The technology described is available to all service companies, including those without the internal product development capabilities who previously relied on third party equipment to provide services.

The paper details the design and development of the LWD system which provides borehole compensated resistivity measurements from three sensor spacings. A description of the environmental testing performed on the tools to verify the design, along with the results of field tests in the United States are provided.

Logs acquired during the field test show how borehole compensated resistivity measurements can be calculated and presented without the need for the transmitter antennae to be positioned symmetrically either side of the receiver antennae. This unique antenna spacing design reduces the length of the collar when compared to other resistivity offerings in the industry, potentially enabling measurements to be positioned closer to the bit.

The introduction of the LWD technology for slimhole applications, including horizontal drilling and sidetracking, which contribute a significant proportion of wells drilled within Russia, significantly increases the ability to provide formation evaluation data in real time, enabling optimal well placement within the production zone. In addition, the ability to store resistivity data in memory can potentially reduce the dependency on wireline logging after the well has been drilled.

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