Tight Fractured Reservoirs: a Challenging Environment For LWD Operations Optimization & Fluid Path Detection

Abstract

ABSTRACT The huge number of horizontal wells drilled in complex reservoirs and the development of more accurate logging while drilling (LWD) technologies offer to the oil&gas companies the opportunity to reduce operational risks and save time and costs, by replacing wireline acquisition with LWD tools. This paper describe a new acquisition strategy based on advanced LWD tools recently made available also in 6" hole size. Thanks to this technology it was possible to provide a reliable reservoir characterization and to identify the best fluid path in horizontal infilling wells drilled into tight and fractured carbonatic reservoir. Economic and HSE aspects have been strongly considered in the illustrated strategy. The integrated analysis of advanced sonic and resistive image while drilling logs provided the essential information to quantify the matrix and the secondary fractured porosity as well as the "mixed" porosity, and, in addition, fundamental data to clarify the reservoir quality where Tough Logging Conditions (TLC) cannot be through. The acoustic compressional arrivals contribute to porosity evaluation while the Stoneley waves interpretation allowed the detection of "open" natural fractures. In addition, recognized "open" fractures have been matched with mud losses events, Gas While Drilling and temperature profile. The producible intervals identified by the illustrated methodology agree with the response of the main production results. The approach has been validated by means of an accurate comparison between wireline and while drilling logs response, both available along an interval of a reference well section. The LWD technology has shown its capability to capture the different scale of phenomena occurring into fractured reservoirs. Thanks to the combination of technology, knowledge and people, well data acquisition can be conducted safely and with significant saving in term of operating time reduction. The additional information about fluid path detection can improve the efficiency of the well completion. INTRODUCTION AND SCOPE OF WORK The strong and continuous need to drill and produce high deviated or horizontal wells in the oil business was a heavy impulse to change vision on tool conveyance method moving from Wire Line (WL) to Logging While Drilling (LWD) acquisitions. The service companies in the last years spent a lot of effort in the LWD tool development and now days the quality and the completeness of the last generation LWD is comparable with the wire line technology in most case, and more useful in others. The operators choose the logging data acquisition strategy, while drilling or after drilling, based on project requirements. The LWD tool application not only can provide good performance but can also be an important opportunity to increase efficiency and safety. Few technologies have had a larger impact on these results than Logging While Drilling (LWD).