Type Curves for Vaca Muerta Horizontal Wells

Abstract

The increasing number of drilled, completed, and produced horizontal wells in Vaca Muerta enables strengthening the generation of its type curves. The samples can be categorized by produced fluid, landing zone, and eventually by other criteria, reaching statistical significance and, thereby, enabling the preparation of type curves specific to each criterion. Public domain monthly production data, combined with directional, completion, and hydraulic fracturing records related to horizontal wells in Vaca Muerta, were gathered, building a database that as of December 2017, included 254 wells. Each well was classified according to fluid produced, landing zone, and well location relative to slope breaks of progradant facies. The monthly produced volumes are expressed in equivalent barrels of oil and normalized to 1,000 m of stimulated lateral length. For each class considered, percentiles 90, 50, and 10 of a recomputed monthly series were calculated, as well as the average. The series best-fit theoretical curves were generated and are proposed as type curves. More than 200 new entries were added to a legacy database that had been used to estimate normalized standard production and appraise stimulation trends. In this way, the data sample reached greater statistical significance and included a longer series of monthly production data, making it possible to obtain production type curves with smaller deviation and more robust means and averages. Progress was made in the discrimination of the entire set of horizontal wells in Vaca Muerta by preparing type curves for wells producing black oil, intermediate wet fluids, and dry gas. Production accumulations increase from one production type to the next in the order listed. Relevant to landing zone criteria, discriminated type curves are presented for the "kitchen" (basal section of the formation, which reaches the highest organic and shale content)," the "organic" level (inmediate overlaying section of high organic content), and the lower and the upper prograding facies (shaly limestone sequences in the middle and upper sections of the formation). Particularly for the oil-producing wells, the type curves reveal the increased production in the "kitchen" and upper progradant levels. The elaboration of best-fit curves to the series of typical P90, P50, and P10 data, with its generatrix algorithm, provides a simple aid to approximate production estimates and economic evaluation of projects.