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Hydraulic fractures are traditionally modeled as planar features developed by the tensile failure of the rock. Laboratory nanoseismic and field mine-back studies show that most of the fractures are non-planar complex features. Fracture properties are strongly affected by the magnitudes and directions of the stresses in the formation. Low stresses are associated with a complex fracture development while high stresses create simpler, straighter and more planar fractures. We report the results of controlled laboratory triaxial hydraulic fracturing experiments instrumented with piezoelectric sensors. We performed tests on Lyons sandstone which was determined to have an initially isotropic velocity structure. The fracturing experiments have been performed under triaxial stress state to replicate the insitu stress reservoir conditions. The uncertainty in hypocenter locations, frequency analysis, source mechanisms and the effects of stress on fracture propagation will be discussed. Microscopic observations of the fractures are correlated with the mapped microseismic events. Fractures are observed to be non-planar visually and at the SEM scale. Shear failure recorded by focal mechanisms appears to dominate the failure mode. The deviation from planarity will surely affect proppant transport and dispersement.

Vedanta Ltd, Cairn Oil & Gas operates a tight gas field which produces majorly from the volcanic reservoir. Commercial production is possible post hydraulic fracturing which has been established through successful fracturing campaigns in the past. Hydraulic fracturing in volcanics is a complex operation due to the inherent heterogeneity and associated uncertainty of reservoir properties in these tight formations (~0.1 md). With added challenge of stimulating infill wells landed in partially depleted zones, fracturing becomes the key operation governing the ability to meet production target, project timelines and associated costs. Based on new seismic data obtained during field production and previous campaigns, Cairn executed a development campaign and is now following up with an infill campaign to improve and sustain the production plateau in the Raageshwari Gas reservoir. With consideration of economics of the field development, a strong focus on continuous improvement, optimization and developing the subsurface understanding along with lean and integrated project and contract management strategies to improve operational performance were key to achieving project objectives. A continuous improvement strategy through production technology initiatives was applied to stimulation campaign by re-designing completion, exhaustive data gathering/analysis and optimizing stage count, proppant volume through machine aided data analytics, testing and clean-up time, minimize hookup time to achieve execution targets and accelerate and maximize production time. Proppant onset calculations and well operating envelop were re-defined to ensure longevity to wells. Apart from summarizing the key learnings of the re-development campaign from a petroleum & completion engineering standpoint, the paper would emphasize on the challenges expected & observed and mitigation methods in the infill campaign - the most noticeable of the challenges being depletion. The project resulted in successfully completing 42 wells with ~ 250 frac stages and strategically placing ~ 63 million lb of proppants in gas producing zones. This lead to the production increment of ~ 40% to the overall production which has proven critical to plateau extension. The learnings also form the basis of the future infill campaign. Apart from the technical considerations, the paper would expand on the integrated project management strategies which resulted into achieving volume targets within the assigned budget while managing the local considerations and field specific challenges during the execution phase. This paper lays out a framework on optimized data collection, evaluation and integration for continuous improvement. It maps the uncertainties associated with highly laminated reservoirs and challenges to look at in an infill campaign. Most importantly the Integrated Contract & Project Management framework would provide operators with valuable insights to execute a frac intensive development/infill campaign within the planned budget/resources.

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