Assessment of Reservoir Quality and Maturity using Near-Real Time Surface Measurements: Diyab Source Rock In Abu Dhabi

Abstract

Estimating reservoir potential and placing the well in appropriate zones for production can be complex and challenging in an unconventional play. Diyab source rock located in the United Arab Emirates close to Abu Dhabi is an example of such a complex unconventional. Rise in unconventional exploration is mainly driven by advanced and improved technology. One such advancement in technology is the use of advance surface measurements in unconventional plays at well site which being comprehensive reduces interpretation uncertainty; enabling fast near-real time decision making. Some key inputs in estimating reservoir potential of a source rock play are fluid type, rock texture, lithology, Total Organic Carbon and maturity. Reservoir fluid quality assessment in near real time through compositional fingerprinting of lighter alkanes (C1 - C5), heavy components (C6 - C8), aromatic components (C6H6, C7H8 and MCC6) and non-hydrocarbon components (Helium and CO2). Advanced cuttings characterization at the well site provided minerology quantification using XRD and XRF, texture interpretation using high resolution digital imaging. TOC was measured using the combustion method. Maturity was estimated using a novel technique of diffused reflectance Infrared Fourier spectroscopy. Fluid composition analysis results were used to characterize reservoir fluid type while the rock measurements were used to identify rock litho-facies units. Two main reservoir fluid types were identified in the Diyab source rock. Quantitative surface measurements were available prior to any downhole well logs or lab analysis results. Fluid type analysis was used to aid in the planning of the well logging and core analysis program. Fluid type results were later validated using core measurements. Surface measurements of mineralogy and TOC were compared to the log analysis and core analysis results. An excellent match between the two was observed. Over the interval where core was not available, surface measurements enabled calibration of log interpretation results which were affected due to complex mud additives. Maturity estimation using diffused reflectance infrared Fourier spectroscopy technique was compared to the Vitrinite reflectance (where available) and Bitumen reflectance measurements. A good match was observed between the two.For the first time in Abu Dhabi, a unique workflow of advance surface measurements were adopted to provide near-real-time reservoir fluid composition, quantitative total organic content and maturity assessment in unconventional plays; which enabled us to carry out reservoir quality assessment in the Diyab source rock.Maturity assessments while drilling on cuttings were first ever done in Abu Dhabi.Advance cutting measurements were used in designing core analysis strategy