Optimizing the Development of the Haynesville Shale Lessons Learned from Well-to-Well Hydraulic Fracture Interference
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2017, Unconventional Resources Technology Conference (URTeC). This paper considers different mechanisms of well-to-well interference in low permeability reservoir systems, but focuses specifically on the hydraulic fracture well-to-well interference (commonly referred to as frac-hits) in the Haynesville shale. While well-to-well interference induced by hydraulic fracturing is a very common type of event in this play, such interference is sometimes overlooked as it often results in production gains for the well impacted by the fluids injected during an offset well stimulation treatment. The objective of this study is to maximize the use of the production data available from the well-to-well interference incidents (a simple, low-cost surveillance strategy) to characterize, quantify, grade, and to understand the causes and consequences of hydraulic fracture well-to-well interference in order to continue to optimize the development of the field in terms of its economic value. In this paper we first introduce the different types of well-to-well interference as background before the focus shifts into the hydraulic fracture well-to-well interference. The methodology begins with characterizing, quantifying, and ranking 65 historical frac-hit events that were documented in the Haynesville shale. Following this effort, we describe the findings as to what causes a frac-hit event and what drives the magnitude and extent of the production interference. The analysis of field data lead us to the relatively simple observation that a pressure sink (i.e., an area of depleted pressure) is not only the main cause, but it is also a necessary condition for a significant frac-hit to occur. Data suggests the degree of well communication highly correlates to the magnitude of the pressure sink and the distance between the producer and the infill well. Regarding the well performance implications for the "parent" wells in the Haynesville shale, some wells do experience severe wellbore damage from a given frac-hit (or sequence of frac-hits). Although cases of severe damage are not the focus of this paper, we include insight about such cases and we direct the reader to other sources of information. An obvious comment would be that frac-hits which cause damage are considered to be negative. However, for the majority of the cases reviewed in this paper, the parent wells affected by frac-hits are able to continue to produce - and the post-frac-hit impact varies from neutral to positive both in terms of short-term production gains and long-term recovery. On the other hand, it is clear through analyzing field examples, that new completions hitting legacy wells during stimulation are impacted in a relatively negative way as the conductive pathways created through hydraulic fracturing grow into preferential planes of less resistance into existing offset producer(s) - instead of enhancing additional matrix near the infill well(s). These conditions often translate into lower initial pressures, and thus, an overall lower recovery for those wells relative to comparable infill wells that did not connect significantly with parent wells. We also share some observations regarding overall section recovery in the context of frac-hits. As for preventing the negative impact of frac-hits in instances when stress barrier is not a possibility, one of the alternatives we propose is to evaluate (in terms of well integrity and economics) refracturing the parent well before any infill activity as means to (1) protect the wellbore and remaining reserves of the parent well, (2) potentially increase recovery in the parent well or accelerate volumes, (3) minimize negative effects related to well performance and recovery in the infill wells due to possible pressure losses from the new completions into depleted areas.
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Proceedings of the 5th Unconventional Resources Technology Conference
