Optimizing Vaca Muerta Completion Strategy using a Geomechanics/Petrophysics Centric Stimulation Workflow, Neuquén Basin, Argentina
Senior Production Stimulation Engineer, Schlumberger Argentina S.A.
Introduction—Producing commercial quantities of hydrocarbons from shales was uncommon a couple of decades ago but successful developments in North America and recent exploration and appraisal activity around the world has changed the future outlook of the oilfield industry. Considering, shales represent the most abundant form of sedimentary rock on earth even countries that have little current hydrocarbon production have great interest on shale exploration in order to recover their hydrocarbon self sufficiency. The specific shales that are of special interest are organic-rich sedimentary rocks that acted as source rock and seals for hydrocarbons that accumulated in porous over/underlying reservoirs. The migration of hydrocarbons out of source rocks into permeable formations took place over geologic time frames but if sufficient hydrocarbon remained in the rock after the migration process then the organic-rich shale becomes potentially productive. Depending on the thermal maturity of the shale, the hydrocarbon could be either oil or wet gas or dry gas. Each shale play is unique in nature with respect to its depositional environment, mineralogy and production drivers so they require good reservoir understanding, optimum completion strategy and tailored fracture stimulation for success. Failure of any of these key aspects could be translated to a marginal or uneconomic well.
This work presents an efficient, yet detailed, integrated workflow of petrophysics and geomechanics data coupled with complex fracture models, single-well completion strategies and fracturing stimulation techniques for the Vaca Muerta Shale Play located at the Neuquén Basin in West-Central Argentina.
Reservoir Centric Stimulation Workflow—It is an established fact that due to its relative low to ultra-low permeability, organic-rich shale reservoirs can produce neither at economical flow rates nor in economical volumes unless the well is stimulated via a hydraulic fracture treatment. It is also well known that both flow rate and volumes after stimulation are linked to properly identify and stimulate the hydrocarbon prolific shale zones and the extension of the complex fracture network that could be potentially generated during the fracturing stimulation treatment.
In order to identify the most hydrocarbon prolific shale sections and maximize the generation of the complex fracture network, the integration of various disciplines such as Geomechanics, Petrophysics and Stimulation must be addressed in order to develop a reservoir-centric stimulation workflow that will give us an optimum completion strategy and stimulation design as the final output. The application of this integrated workflow would identify and determine the key parameters that directly impact the productivity of the shale reservoir allowing us to reveal the true potential of the well after the fracturing stimulation treatment.
The reservoir centric stimulation workflow for the Completion Strategy and Stimulation Design of unconventional reservoirs is based on identifying two critical parameters which are the Reservoir Quality (Petrophysics Evaluation) and Completion Quality (Geomechanics Analysis) that combined by using the completion advisor of the Unconventional Stimulation Design Software4 results in a Composite Quality Index that highlights the specific zones with optimum Reservoir Quality and Completion Quality in which the perforation clusters will be placed, it also defines the number of fracturing stages to ensure optimum zone coverage and enhance reservoir contact. Once the optimized completion strategy is defined, the petrophysics and geomechanical data is shared through the single platform of the Unconventional Stimulation Design Software in order to obtain a tailored fracturing stimulation treatment by modeling the placement of the fracturing schedule in a non-planar complex fracture network simulated either in the wire mesh model or the Unconventional Fracture Model.
Reservoir Quality (RQ)2: Is a measure of productivity and transmissibility of the formation that allow us to identify the most hydrocarbon prolific zones which are determined by the petrophysical data such as organic content, thermal maturation, effective porosity, intergranular porosity, permeability, fluid saturations, mineralogy, pore pressure and hydrocarbons—in place. Core data, wireline open hole logs, magnetic resonance and elemental capture spectroscopy sondes are commonly used in this step as input for the petrophysical evaluation.
Completion Quality (CQ)2: Is a measure of the ability to initiate, propagate and sustain a conductive fracture determined by the geomechanical data obtained through sonic logs, core data and a 1D Mechanical Earth Model (MEM) which is built by properly quantifying and qualifying critical parameters such as near-wellbore and far-field stresses, Young’s Modulus, Bulk Modulus, Shear Modulus, Poisson Ratio, proppant embedment, natural fractures/faults density and orientation, induced fractures and breakouts azimuth and other elastic properties needed to define the CQ and the non-planar fracture complex geometry.
AAPG Search and Discovery Article #90165©AAPG 2012 GEOSCIENCE TECHNOLOGY WORKSHOP, 2-4 December 2012, Buenos Aires, Argentina