Sweet Spots in Vaca Muerta: Integration of Subsurface and Production Data in Loma Campana Shale Development, Argentina

Day 2 Thu, June 02, 2016

2016

In organic shales, hydraulic fracturing is an important parameter to optimize production of horizontal wells. For a lateral standalone, propped surface should be maximized to increase production (by increasing total proppant per well). While in the case of a pad, well spacing is an additional constrain for hydraulic fracture dimensions not to overlap with hydraulic fractures of neighboring offsets. Competition for production between laterals of a given pad should be minimized and is the result of both well spacing and hydraulic fracture design. A numerical model coupling an explicit description of the hydraulic fracture geometry and reservoir simulation is proposed. Fracturing simulator accounts for material balance, geomechanics, interaction with natural fractures and stress shadowing within and in between fracturing stages. Production interference is evaluated by comparing forecasted production of a lateral standalone (single well approach) against this same lateral while surrounded by offsets competing for production (multi well approach). Sensitivities are run assuming different completion and well spacing scenarios varying different parameters such as fluid and proppant volume, fracturing fluid type and staging. Production interference between horizontal wells might reduce the final recovery of each individual well. However it provides an opportunity for simultaneous optimization of completion and well spacing to guide field development. Hydraulic Fracture dimensions must match well spacing. Variation of fracture geometry along the lateral should be accounted for to evaluate well spacing and prevent the excessive growth of one single facture within a given stage. Completion design can be engineered by adjusting hydraulic fracture treatment volume, perforation cluster spacing or fracturing fluid viscosity to increase the overall consistency of the resulting fracture geometry and reduce effect of production interference between laterals of a given pad. Novelty of the proposed methodology relies on the explicit description of the hydraulic fracturing geometry and direct coupling with reservoir simulation, not only for a single well, but considering a whole pad of horizontal wells as per a possible development of the Vaca Muerta shale.

Completion and Well Spacing Optimization for Horizontal Wells in Pad Development in the Vaca Muerta Shale

Suarez¹,

Day 2 Thu, June 02, 2016

2016

Fracturing-to-Production Integrated Completion Sensitivities for Horizontal Well Design in the Vaca Muerta Shale

SPE Latin America and Caribbean Petroleum Engineering Conference

Cafardi

Cavazzoli

et al. 2017

The boom of organic shale plays has revealed the critical need to correctly size hydraulic facture treatments to achieve commercial success in those reservoirs. The right balance must be found between the cost of fracturing and the additional production achieved by increasing the formation-to-wellbore contact area. Such a balance is formation specific and depends on the reservoir properties and local well completion costs. This paper examines a wide range of completion scenarios to evaluate the relationship between hydraulic fracture design, production, and well profitability using numerical simulations to guide completion of horizontal wells in the Vaca Muerta shale. Evaluation of the interaction between completion and production requires an integrated approach including both static (petrophysics, geomechanics, and the characteristics of natural fractures) and dynamic (reservoir fluid, conductivity degradation, and reservoir pressure) properties. The hydraulic fracture geometry is determined using a state of the art simulator that models the physical mechanisms of elastic deformation, leakoff, proppant transport, and the interaction between hydraulic and natural fractures. The explicit description of the hydraulic fracture geometry ensures that any variation in the completion design is consistently taken into account. Hydraulic fracture geometry is then directly fed into a reservoir simulator to evaluate the anticipated production. The resulting production profile is then input to an economic model to assess the profitability of the proposed scenario. The model is based on the latest understanding of the Vaca Muerta shale and is calibrated by reproducing the average historical production of the play. A sensitivity study is performed to investigate the impact of each completion parameter. Proposed sensitivities consider a large range of completion design parameters for a horizontal well, such as the type and volume of fracturing fluid and proppant, number and spacing of perforation clusters, and staging strategies. The sensitivity analysis covers more than 60 completion scenarios over 550 fracturing stages and 1,600 individual hydraulic fractures. All the simulation cases are combined in a database to quantitatively evaluate the impact of completion design over the hydraulic fracture dimensions and production, and highlight its main contributors. Total volume of proppant per well and perforation cluster spacing show a good correlation with production. This production increase can be linked with an increase of the propped surface highlighting the need for the right balance in between fracturing fluid viscosity to enhance transport and the proppant concentration to compensate for total treatment volume. The results of this study provide practical guidelines for optimizing completion of horizontal wells in the Vaca Muerta shale.

Flowback-Based Minimum Stress Estimate in Low-Permeability Environment: Procedure, Interpretation, and Application in the Vaca Muerta Shale

Day 1 Tue, January 23, 2018

Varela²,

Manière

et al. 2018

Low-permeability formations must be hydraulically fractured to produce at commercial rates. A good understanding of the formation stress conditions is critical for completion design, but requires in-situ measurement as calibration to support the geomechanical evaluation. This calibration is commonly done using diagnostic formation injection test (DFIT) methodology by creating a hydraulic fracture and then waiting for it to close through leakoff to the formation. However, in a low-permeability low-leakoff environment, application of this approach might become limited because of the time to fracture closure and the non-uniqueness of the interpretation. This paper demonstrates the applicability of the fracture flowback method to define closure pressure. Although proposed in the 1980s, this method has been underused by the industry. One of the objectives of this paper is, therefore, to advocate through field examples its simplicity of development, interpretation, and repeatability, particularly in low-leakoff reservoirs such organic shale formations. The procedure is composed of a sequence of various cycles of pump-in flowback through a fixed choke, pressure rebound, and fracture reopening. The proposed methodology offers several minimum stress measurements for repeatability and quality check purposes, reduces interpretation non-uniqueness, and can be completed within 1 hour, making it compatible with the hydraulic fracturing operations. Test design considerations, such as well geometry, pump rate, fluid volume, choke size, or perforation requirements, are reviewed to maximize the chance of success. Interpretation of the different possible patterns that can be observed is discussed and illustrated with practical examples from the Vaca Muerta shale. Comparison is made between the pump-in flowback and calibration decline approaches performed over the same interval. Repeatability is evaluated, and discrepancies between cycles are investigated. A direct application of the method is the calibration of a stress profile when applied to a vertical well. However, additional observations related to the fracture closure mechanism or residual fracture conductivity can be drawn by detailing the flowed-back volumes or rate of rebound pressure. These observations can be related to the lithology when the procedure is implemented in different intervals of the same formation.