Integrated Methodology for Laboratory Evaluation of Shale Plays Cores

Abstract

In the last 10 years, shale gas has emerged as an alternative source because of its contribution to oil and gas reserves. Colombia has a high hydrocarbon potential in unconventional shale gas deposits, and this become the main objective of the national oil industry. Currently proven reserves of conventional gas in Colombia are about 6 TCF, while technically recoverable reserves of shale gas according to the US. Energy Information Administration (EIA) studies 1 are about 55 TCF, so successful production of these reservoirs will increase significantly gas reserves in Colombia.Ecopetrol was the first company in Colombia in starting the characterization of unconventional shales through the stratigraphic well La Luna-1 located in the Medium Magdalena Valley, from which 3445 feet of core were recovered in five months between 2011 and 2012.The need for interpretation frameworks in order to understand properties such as rock source quality, mechanical properties and production performance from a diverse range of measurements require a laboratory characterization of rock properties that is an important part of any resource evaluation. This was the challenge for the labs of the Colombian Petroleum Institute, that based in its experience in Conventional reservoir analysis could adopt its skills and methodologies for analyze 2851 rock samples. The work flow includes geochemical analysis for Total Organic Content (TOC), Pyrolysis Rock Eval VI (parameters S1, S2, Tmax) and quantification of gas content (canister). Samples selection for other analysis was based on core Tomography and Spectral Core Gamma. From the same foot of core, the samples were taken for petrographic analysis, quantitative mineralogical analysis by XRD, mineral distribution and microtexture by SEM, geomechanical Analysis (elastic module and the rock strength), basic petrophysical analysis and Mercury Injection Capillary Pressure (MICP). The information obtained was integrated in order to obtain petrographic rock types, hydraulic rock types and identify the most prospective intervals. The coherence in the parameters obtained by different methods demonstrated the sturdiness of quality system and methodologies applied.

Sweet spot areas for shale oil and shale gas plays in the Upper Cretaceous rocks of the Middle Magdalena Valley, Colombia: insights from basin modeling

“…In all cases, clays content is lower than 40%, suggesting, that most of the units have an excellent brittleness quality which might help in future completion designs, also agreeing previously published petrophysical models which proposes at least two landing zones within the Salada and Galembo formations (e.g., Piedrahita and Aguilera, 2017a;Veiga et al, 2023). Perez et al (2014) presented an XRD dataset of the La Luna-1 well, showing the composition of clay minerals. Their results show that illite and interstratified species compose the bulk of the clay minerals and have lesser proportions of kaolinite.…”