The use of horizontal wells and multistage fracturing that is currently common in unconventional reservoirs first became popular during the early 2000s. Since then, the effectiveness and efficiency of horizontal wells has continued to be recognized. Because of the large number of these horizontal wells, significant opportunities for refracturing exist. Restimulation of these wells can allow the operator to increase production, as well as recoverable reserves, generally more economically than by installing new laterals or by infill drilling. An important challenge in refracturing these wells is to understand the rock system in which the well and the hydraulic fracture system are placed.The major hurdle for net returns on any restimulation is effective candidate selection. This process involves not only choosing the right well, but also choosing the best zones within that well. Often, either a well (or zone) has not produced adequately or has been prolific and is in decline. However, there is no model that can predict production as accurately from unconventional reservoirs as from conventional ones. There are, however, measurable parameters that, when analyzed together, can indicate the relative potential of one zone to another. Therefore, to perform this analysis, any available data on the reservoir should be gathered. Then, well diagnostics are run to fill in the inevitable gaps in these data.This paper discusses using a novel combination of cased-hole logging tools to gather these data. Using this combination to log the well after the first hydraulic fracturing treatment, the optimum restimulation candidate(s) can be determined. Then, whether to use existing perforation locations or to perforate new areas to cover non-stimulated rock can be decided; thus, optimizing the refracturing process. This selectivity of both candidates and zones during the refracture design can save time, costs, and resources, increasing the economic efficiency of the operation.

This paper discusses how applied science, historically safe operations, advancements in technology and standard processes are helping to address and reduce environmental issues (EI) for hydraulic fracturing in shale gas wells. The technologies presented include equipment footprints allowing for a reduced risk for environmental effects, 3D fracture mapping, microseismic fracture mapping, "green" fracturing fluids, bacteria control through UV light technology and an improved method of water recycling. This combination of scientifically-derived technologies and best practices (a.k.a standards) is assisting in lowering the risk for EI and addressing misconceptions about hydraulic fracturing. To further address these environmental issues, members of Oil & Gas (O&G) industry associations, including the American Petroleum Institute (API), Society of Petroleum Engineers (SPE), International Association of Drilling Contractors (IADC) and the International Association of Oil & Gas Producers (OGP) based in London and Brussels, continue to develop sound science and field-proven best practices in the form of industry standards, such as those referenced in this paper. Technical publications by O&G service companies have provided numerous case histories highlighting these applicable technologies. These presented technologies and practices have helped to demonstrate the positive impacts for shale gas development projects.

A new generation of ultradeep wells has significantly increased in Saudi Arabia in green and brown field developments. One ongoing complex field development is the Manifa field, which is located in northeast Saudi Arabia. Manifa is probably the largest extended reach hydrocarbon producer project globally, with more than two-thirds of its 350 wells being extended or mega reach wells. The offshore portion of the field contains 83 developed wells in 13 platforms with openhole sections within the range of 3,000 to 9,000 ft, where acid stimulation intervention is necessary to remove reservoir damage and to help improve well performance after drilling operations. Although the openhole completions provide superior deliverability, a primary challenge remains with respect to rigless intervention.The offshore platforms have limited deck load capacity and available deck space necessary for performing coiled tubing (CT) stimulation operations. To overcome these constraints, applicable CT operations from a jackup barge combined with a support pumping vessel were introduced and subsequently developed to allow well interventions using large treatment fluid volumes.This paper describes CT stimulation campaigns performed on extended reach horizontal wells in the Manifa field. A summary of the steps involved during an improved CT intervention technique successfully implemented within this field to access some of the longest openhole horizontal wells is presented. The importance of a combined application of jackup and stimulation vessel units to help ensure safe project execution on offshore platforms is reviewed.

Abrasive fluids have been applied in mechanical cutting and perforating systems for years, the result is a precise cut in any size tubular. In abrasive perforating, the entry hole created reveals no tubular deformation or presence of flow obstructing debris. Consequently, the sand-laden fluid moves past cement, damaged zone or filter cake and into virgin formation. At that instant, velocity generated through the nozzles propagates abrasive fluid into multiple reservoir layers creating numerous pathways. Optimizing the direction of perforations allows for cost effective stimulation through conventional fracturing techniques. Therefore, as an alternative to conventional perforating, oriented abrasive perforating is applied specifically for creating channels to natural fractures. This paper discusses the development of abrasive perforating coupled with orienting technology for penetrating tubing, casing, drill collars, and drill pipe, all of which is deployed using coiled tubing or jointed pipe in re-completions. In addition to conventional coiled tubing tools, this system utilizes an engineered weight bar connected to a high velocity perforating sub. This paper begins with the development of this technology and existing perforating methods, then a description of tests conducted with the abrasive perforator and subsequent results. Benefits and applications with applied case histories are also discussed including multiple stage plug setting and perforating as well as pipe recovery, followed by conclusions and recommendations. Development of Technology Based on evolving requirements from Oil and Gas Operators, the need to develop a more economical perforating system arose. As wells with larger horizontal sections are completed, the inability to reach zones of interest further substantiates the use of coiled tubing and related tools. This technology was developed from using abrasive fluids to cut tubulars with a motor and high velocity cutting head 1. Currently, wells are perforated using explosive means such as Tubing Conveyed Perforating (TCP) and Electric line. Although these systems are industry standard, challenges and limitations such as extensive rig-ups, the presence of debris post firing and restricted ability in extended horizontal sections do exist. While both systems have been around for years, their inability to completely orientate perforations is inherent. To maintain simplicity, this system utilizes conventional thru tubing equipment allowing for jet orientation using an engineered weight bar placed below a free rotating swivel joint as illustrated in Figure 1. The engineered weight bar is eccentric based, allowing for weight transfer to the low side of the tubular as shown in Figure 2. This method of application was referenced from a registered patent, describing single trip wellbore isolation and oriented perforating 2. Based on pump rate and pressure, orifice selection is crucial to maximize jetting velocity. Hydraulic calculations determining pressure drop and velocity at the exit point allows for precision cutting. For example with one 0.125inch orifice, maintaining a pump rate of 0.5bbl/min at 2500psi produces an exit velocity of 540ft/sec. The sand slurry is not fully abrasive until it enters the orifice gaining momentum at which point the stage of abrasion commences. The 100mesh particles recommended exhibit less momentum in non-divergent fluid streams and consequently less damage to the inside of the coiled tubing. In a jet stream, smaller particles retain impact/kinetic energy through reduced mutual interference 3.

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