| Abstract |
Geothermal energy, a promising and sustainable alternative to fossil fuels, relies on the efficient drilling and operation of geothermal wells. Drilling these wells encounters numerous formidable challenges that can give rise to unanticipated expenses and hazards. Swelling clays like smectite, pose substantial impediments during the drilling process and wellbore development within the Olkaria geothermal field. These impediments include incidences such as bit balling rendering penetration practically impossible, differential sticking, wellbore collapsibility, and an escalation in unproductive time. Various methodologies for identifying these minerals have been established, yet their utility in addressing this predicament remains largely unexplored. Notably, the existing techniques for mineral identification, such as laboratory X-ray diffraction (XRD) analysis of well logs, are both time-consuming and unsuitable for real-time monitoring. The present methodology in use for the on-site detection of swelling clays involves the application of the methylene blue test. However, this method is constrained by its subjective nature, semi-quantitative character, specificity to particular clay mineral types, and its incapacity to provide comprehensive structural information. Infrared Spectroscopy (IR) enables the analysis of the interaction between matter and electromagnetic radiation in the infrared portion of the electromagnetic spectrum. The advantages of IR spectroscopy lie in its ability to provide on-site, real-time data without the need for time-consuming sample transportation to a laboratory. Spectral signals from SWIR spectroscopy can be utilized to identify and quantify various clay minerals within the drill cuttings, enabling geothermal operators to make informed decisions promptly. This method offers the potential to streamline drilling operations, improve casing design, and reduce non-productive time, ultimately contributing to the success and sustainability of geothermal energy projects. For this research, geothermal drill cuttings obtained from wells OW 922, OW 925, and OW 740 in the Olkaria geothermal project in Kenya were subjected to dual analytical techniques, namely X-ray diffraction (XRD) and infrared (IR) spectroscopy. Initially, XRD analysis served to confirm the presence of swelling clays within the well samples. Following this confirmation, the samples were subsequently subjected to IR spectroscopic analysis. During the IR spectroscopic analysis, characteristic Hydroxyl (OH) Stretching Bands, which are commonly associated with swelling clays (Smectite), were distinctly observed as absorption bands within the shortwave infrared (SWIR) region, falling within the spectral range of 1.4 to 2.5µm on the electromagnetic spectrum. Ferrous (Fe2+) absorption bands were additionally identified at around 2.3µm, providing evidence of the existence of nontronite, a distinct variety of smectite clay mineral. Sample preparation and measurements for IR is simpler and faster. It involves little to no sample manipulation. Hence very optimal for real time. This observation underscores the applicability and effectiveness of IR spectroscopy as a viable real-time method for the detection of swellings clays during the process of geothermal well drilling |