This paper continues the investigation of interwell fracturing interference for an infill drilling scenario synthetic case based on Eagle Ford available public data and explores pressure and stress-sink mitigation strategies applied to the simulation cases developed in the previous publication (SPE 174902). Emphasis is given to refracturing scenarios, given the intrinsic restimulation value for depleted parent wells and the strategic importance due to the current low oil prices. The stress and pressure depletion methodology is expanded in this paper, adding a refracturing scenario before the infill child well is stimulated. Changes in stress magnitudes and azimuths caused by new and reactivated fractures are calculated using a finite element model (FEM). After refracturing the parent well, modeling shows that stress deflection and repressurization of the originally depleted production zone will reduce subsequent fracture hits from infill wells. The first mechanism to reduce fracture hits is the stress realignment, which promotes transverse fracture propagation from the infill well away from the parent well. The second fracture-hit-reduction mechanism is repressurization of depleted zones to hinder fracture propagation in lower-pressure zones. Prevention of fracture hits by active deflection results in an increased stimulated reservoir volume (SRV) for both the parent and child wells. Overall pad level and individual wellbore cumulative production experience a significant increase due to increased SRV. With proper reservoir and geomechanical data, this approach can be applied in a predictive manner to decrease fracture-hit risk and improve overall recovery. This workflow represents the first comprehensive multidisciplinary approach to coupling geomechanical, complex hydraulic fracture models, and multiwell production simulation models aimed towards understanding fracture-hit reduction using refracturing. The workflow presented can be applied to study and design an optimum refracturing job to prevent potentially catastrophic fracture hits during refracturing operations.

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In the past decade the industry has embraced unconventional resources; namely, shale oil and shale gas. After the initial drill-to-hold stage, multiwell pad drilling and stimulations are employed to exploit the acreage. Zipper fracturing is a technique that reduces the standby time (up to 50% reduction, when combined with the plug-and-perf isolation method). Because of this operational efficiency improvement, zipper fracturing has become one of the most common fracturing practices for unconventional reservoir stimulation. It has also been purported to increase production, which several authors have previously reported. There are also other studies showing no benefit of zipper fracturing on production performance.In this paper we have used a complex fracture network model, which we refer to as the Unconventional Fracture Model (UFM), to study zipper fracturing. The model simulates complex (branched) fracture propagation, associated stress shadows, fluid flow, and proppant transportation in the complex fracture network. The model solves the fully coupled problem of fluid flow in the fracture network and elastic deformation of the fracture. A key difference between UFM and the conventional planar fracture model is being able to simulate the interaction of hydraulic fractures with preexisting natural fractures (also referred as planes of weakness). The UFM simulates interwell and interstage stress shadows and honors both sequential fracturing and zipper fracturing scenarios' geomechanical interaction.In this paper, we present the results of a zipper and sequential fracturing study that includes the completion design optimization and the associated production performance in the Eagle Ford Shale. The study provides a workflow to optimize the completion and stimulation designs in pad development and to improve rate of return. The quantitative results show that zipper fracturing may not deliver a production benefit when compared with sequential fracturing and is a function of well spacing and perforation cluster spacing in a given area.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWhile the hydraulic fracturing of vertical wells is perhaps the most widely used method for production/injection enhancement in the petroleum industry, the fracturing of horizontal wells has been used sparsely, mostly in the United States and the North Sea. Usually this involves either longitudinal fractures or treatments with no regard to the well orientation and fracture azimuth. A new abrasive jet cutting tool has now been designed and built specifically for this type of jobs.In this paper we will present all the design and operational challenges that will be faced in such fracturing project, and make recommendations for successful treatments

Fracturing has become ubiquitous in the petroleum industry to the point that, at least in North America, almost all natural gas and the vast majority of oil wells are fractured. In fact there are more fracturing treatments than there are wells because of multiple treatments in many wells. Because of recent activities in shale gas, hydraulic fracturing of horizontal wells has become increasingly popular. However, not all reservoirs lend themselves to the same fracture and well architecture. Other than deviated wells which we do not recommend, to match proper well architecture (vertical versus horizontal) and number and size of treatments is a very important production engineering exercise. For gas wells one of the most important additional considerations is turbulence which happens in two places: the reservoir and then in the created fracture. This paper will discuss production from vertical, horizontal transverse and horizontal longitudinal fractured wells. Calculations of the incremental performance of each configuration are done for both oil and gas wells, using rigorous models for fractured well performance. There are physical and economic limits and criteria. For example, for gas wells in reservoirs above 0.5 md, there is an unacceptable reduction in the performance of each transverse fracture because of enhanced turbulence effects. In such case a vertical fractured well is preferable. There are also economic criteria for selecting which type of completion is the optimum choice. Very low permeability reservoirs while attractive in North America with its controlled costs, they may be very unattractive in other countries. We look at a range of reservoir and proppant pack permeabilities and discuss the optimization of fracture geometry. The paper not only delineates areas of indicated application of each well completion but it highlights the importance of considering the hydraulic fracturing process from the very start of wellbore planning. The processes involved in planning a wellbore for efficient decision making and maximum flexibility of choice are also described.