Barrow Island's Windalia reservoir is Australia's largest onshore waterflooding operation and has been under active waterflood since 1967. The highly heterogeneous reservoir consists of fine-grained, bioturbated argillaceous sandstone that is high in glauconite clay. The high clay content results in a low average permeability (5 md) despite high porosities (25-30%) and hence fracture stimulation is required to achieve economic production rates.The Windalia reservoir and fluid properties preclude the use of traditional EOR technology, with thermal, miscible and mobility control processes all deemed unfeasible through screening studies. Consequently, the in-depth flow diversion mechanism was developed and applied, which utilizes a low molecular weight polymer to drive the growth of induced hydraulic fractures in the treated injection wells. A 3-injector pilot was executed involving polymer injection for two years, with no detrimental injectivity losses observed for polymer concentrations up to 750 ppm. Considerable fracture growth, oil production rate uplift and reduction in water cut were observed throughout the pilot pattern, in line with predictions: Fracture half-lengths increased from 6 ft to 400 ft in one injector and from 141 ft to 322 ft in another  An initial oil rate uplift of 38% relative to the production baseline was observed; a more conservative estimate suggested that at least half of this was attributable to the tertiary recovery process  The water-oil ratio was observed to fall from 15 to 11, similarly timed with the oil production increase.These improvements were observed consistently throughout the pilot area and were distinct from the waterflood behavior elsewhere in the field. This paper briefly summarizes the technology screening and pilot execution stages, after which the results from the pilot are presented and discussed. This technology may be of use in other low-permeability waterfloods with induced injector fractures, for which traditional EOR practices are believed to be unfeasible.

Petroleum Experts' Integrated Production Model (IPM) suite of software is widely used in the E&P industry especially for project evaluations that require integration of both surface and subsurface models. There is evidence in the literature to show diverse applications in field development planning, integrated forecasting, surveillance and production system optimization. Perhaps less reported are the lessons learned and best practices in using the IPM software. This paper focuses on these issues using Chevron's IPM model for some of its largest gas fields.The Non-Operated Joint Venture (NOJV) Subsurface Team began developing an IPM model for one of its biggest gas assets in 2005. With explicit modeling of critical components like compressors, dozens of wells and reservoir tanks, platforms, fluid characterisation, gas-water contact movement, pipelines, sub-sea manifolds and separators, this is arguably the largest and most complex IPM model in Chevron. The model continues to play a critical role in Chevron's effective capital stewardship of the gas asset. The need to maintain the credibility of this model cannot be over-emphasized, and the model has undergone several phases of enhancement to ensure that it continues to meet business objectives.This paper describes some of the best practices and lessons learned in constructing and maintaining a complex IPM model. It is intended as a resource for IPM practitioners. Examples cover all aspects of the IPM from the non-technical (e.g. framing the problem, case definition and naming convention) to the technical (e.g. model construction, model maintenance, software limitations, constraint violations, production optimisation and quality assurance checks). IntroductionProduction forecasting involves attaching a timescale to production recovery and it is one of the most vital roles of reservoir engineering. It underpins the cashflow of any project and can make the difference between a project being sanctioned or abandoned. The complexity of the role is underscored by the requirement to integrate multiple and diverse disciplines including subsurface characterisation, surface network configuration, production philosophy, economic limits, business decisions and operational constraints.Unlike production forecasting for oil fields, gas forecasting is further complicated by long-term contracts and the need to meet contractual obligations. This requirement means that gas companies need to correctly predict the execution of future projects to ensure that they have enough gas to satisfy their contractual oligations. Usually, in gas forecasting, multiple fields with diverse fluid properties are produced simultaneously and this further introduces the complication of gas quality whilst also maximizing the value of by-products like condensate and natural gas liquids. These complexities indicate that an integrated gas forecasting model is required to accurately predict production for a gas field. There are many such products available including company proprietary software for internal us...