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Hydraulic fracturing, when applied in concert with horizontal drilling, has led to a rejuvenation and revolution in the oil and gas industry that has been felt globally. When once development and reserve addition opportunities in the US were deemed to be very limited now technically recoverable reserves for both oil and gas in the US are viewed as abundant, and long-lived (EIA 2016). Yet hydraulic fracturing itself relies on the placement of proppants and the performance of those proppants to succeed. The earliest hydraulic fracture stimulations utilized poorly sorted river sand as proppant. Since this first experiment with proppants, the industry has evolved with a broad range of proppant choices although natural sand of some type remains by far the proppant of choice for a variety of reasons. Technology has advanced in many ways since the first fracture stimulation. For the past thirty years, the Stim-Lab Proppant Consortium has engaged in a continuous program of building knowledge and understanding in the behavior of all types of proppants used in hydraulic fracturing. Arguably no other body of knowledge about proppants exists that compares in extent and detail with that accumulated by the Consortium. There are many basic understandings about the behavior of proppant packs under downhole reservoir conditions that have been developed through thousands of tests that have been performed through the work of the Consortium. These include the effects of proppant type, grain failure, fines migration, embedment, non-Darcy and multi-phase flow, cycling, loading, packing arrangement, fracture fluid damage and others. All of these effects can be at work simultaneously to negatively affect flow in the propped fracture and the recognition of these effects assists to explain observed well performance. This paper will present basic understandings of proppant performance that are sometimes misunderstood or wrongly applied and will assist the practicing engineer in well diagnostics and stimulation design. It will also present and describe predictive performance models developed for proppants that in turn leads to the most comprehensive simulation of proppant performance under realistic downhole conditions available in the industry.

The proportion of persons with neurotic personalities in flats was not significantly greater than that in houses. Extraversion was not correlated with psychiatric illness or with the tendency to consult a doctor. Flat dwelling, but not house dwelling, was sufficient stress for neurotic personalities to cause, among them, an increase in clinical psychiatric illness. The resulting increase in the overall level of psychiatric illness of all flat dwellers was too small to be significantly greater than that of all house dwellers.

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About 3ieThe International Initiative for Impact Evaluation (3ie) promotes evidence-informed equitable, inclusive and sustainable development. We support the generation and effective use of high-quality evidence to inform decision-making and improve the lives of people living in poverty in low-and middle-income countries. We provide guidance and support to produce, synthesise and quality assure evidence of what works, for whom, how, why and at what cost.3ie evidence gap map reports 3ie evidence gap maps are thematic collections of information about impact evaluations or systematic reviews that measure the effects of international development policies and programmes. The maps provide a visual display of completed and ongoing systematic reviews and impact evaluations in a sector or sub-sector, structured around a framework of interventions and outcomes.The evidence gap map reports provide all supporting documentation for the maps, including thematic background information, the methods and results, protocols, and analysis of the results. About this evidence gap map reportThis report presents the findings of a systematic search to identify and map the evidence base of impact evaluations and systematic reviews of interventions that aim to promote energy efficiency and energy conservation.