Wellsite Geochemistry - New Analytical Tools Used To Evaluate Unconventional Reservoirs To Assist In Well Construction And Smart Completions

Tonner, David (Weatherford International Ltd) | Hughes, Simon (Weatherford International Ltd) | Dix, Michael (Weatherford International Ltd)



 New field deployable analytical techniques for measuring hydrocarbon pyrolysis, organic carbon content, inorganic elemental analysis of rock and mineralogy, and mud gas are proving to be very useful when drilling and completing shale wells. Experience in different shale plays have shown that these techniques can be used to assist in predicting fluid type, delineating potential pay zones and compartmentalization for strategic placement of fracturing stages based on rock and chemical properties. A combination of techniques involves an instrument for mobile programmed pyrolysis (PPy) which uses drill cuttings to evaluate residual oil content in source rock (S1), remaining hydrocarbon generation potential (S2), thermal maturity (Tmax) and total organic carbon (TOC). A semi-permeable membrane probe extracts and analyzes real-time hydrocarbon (C1 – C8, benzene, and toluene) and non-hydrocarbon gases (CO2, N2) dissolved in the drilling fluid. Drill cuttings are also collected and evaluated onsite using X-ray fluorescence (XRF) and X-ray diffraction (XRD), which provides an elemental breakdown of the composition of the rock and the mineralogy. The elements can be used to create a chemical Gamma ray log, estimate TOC and identify mineralogy and brittleness. In unconventional reservoirs, such information can aid in the delineation of pay zones and be used to design horizontal completion and stimulation programs. This data is calibrated and integrated with ground truth core measurements and wire line log data to provide more comprehensive formation evaluation while drilling. Logging horizontal wells using downhole tools involves considerable engineering challenges and costs. Rugged, portable, surface-based technologies deployed at wellsite offer a cost-effective and lower-risk alternative for reservoir characterization. The examples presented in this paper demonstrate how surface analytical instruments can provide real-time insights into stratigraphy and reservoir characteristics during drilling of horizontal wells, and how those insights can be used to improve completions and hydraulic fractures.