With the persistent tightening of global oil and gas costs, operators have been forced to find more economical drilling, completions, and production processes. This trend has impacted the low-budget economics of unconventional producers more so and operators now seek more cost-effective means to understand a reservoir in terms of geology, geochemistry and geomechanics, compared to traditional and more expensive downhole logging tools.
This paper reports an integrated formation evaluation workflow on a multi-well case study in the Northern Delaware Basin using surface logging and laboratory analyses only. We will present how this approach provided subsurface characterization for enabling key drilling and completion decisions and optimizing future well planning and target selections.
A general plan for any field may include a complete set of analyses for a first "training" well. Data acquired are interpreted through a variety of statistical tools to tailor the best technique combination to well planning, drilling and competition strategies for specific targets. Following wells and produced oil samples will then help to refine the applied approach for an overall optimized operational and production strategy. Compositional (C1-C8) and carbon isotope (C1-C3) analyses were carried out on mud gas, while drill cuttings were screened for mineralogy (XRF, XRD) and fluid (thermal-extraction gas chromatography, GC-MS). The integration of data acquired at well-site while drilling and laboratory measurements from both drilling and post well production samples completed the study.
In this study, three potential productive layers, i.e., Avalon, 2nd Bone Spring Sand and 3rd Bone Spring Sand, are investigated in vertical heterogeneities to select optimal landing for laterals, to help refine the completion strategy and give preliminary info on production potential.
Heterogeneities include mineralogy markers, fluid richness, fluid maturity and potentially occurred alterations. A first screening of fluid heterogeneities consists in the use of TE-GC to select the best samples for a deeper investigation through GC-MS. This approach allowed us to observe that the Avalon has a greater vertical variability in fluid heterogeneity, while the evaluation of 2nd Bone Spring vertical section from the first well allowed to monitor the lateral correlation to fluid properties from a second well.
This case study illustrates how integrating cost-effective analyses on surface samples, such as mud gas, drill cuttings and produced oil, can successfully contribute to reservoir description and future well planning. For example, definition of the fluid heterogeneity along a vertical section can help to plan landing points for lateral drilling; screening the vertical profile could also highlight potential secondary targets in the local area. A hybrid solution of field logging and laboratory characterization is a key factor to maintain low costs while preserving the added value; moreover, the structure of statistical data treatment allows the inclusion of new data when additional wells are drilled, with the potential outcome of progressively reducing the number of necessary analyses and costs.
