To date, the art of effective openhole horizontal well fracturing is not well defined. Difficulties in regional sealing hamper the fracturing task, and results are generally suspect. Without proper isolation methods, the use of openhole horizontal well fracturing is limited. During many fracturing processes, including fracture acidizing, fracture or acid placement often occurs where fluid first contacts the borehole, often at the heel of the well. A new method is now available that combines hydrajetting and fracturing techniques. By using this new method, operators can position a jetting tool at the exact point where the fracture is required without using sealing elements. Unlike other techniques, this new method allows operators to place multiple fractures in the same well; these fractures can be spaced evenly or unevenly as prescribed by the fracture design program. Large-sized fractures can be placed with this method. Because the method is simple, operators can economically bypass damage by placing hundreds of small fractures in a long horizontal section. To enhance the process even more, operators can use acid and/or propped sand techniques to place a combination of the two fracture types in the well. This paper discusses the basic principles of horizontal hydrajet fracturing and how Bernoulli's theorem was used to design a hydrajet fracturing technique. Laboratory test results for the new technique are provided on Page 4. P. 263

Successful fracturing treatment necessitates expensive completion assembly that provides some form of isolation to perform controlled fracturing treatments. Currently isolation is performed mechanically which dictates that isolated interval is very short. This in turn may require that the well is cased, cemented and perforated. This would increase the cost of completion significantly. Another option is to focus the fracturing energy via the use of hydrajetting. In this paper we present another approach that provides a high degree of control on where the transverse fractures will initiate and propagate.The various existing techniques for creating multiple hydraulic fractures along an openhole horizontal well are briefly summarized. Laboratory experiments shedding light on some of these techniques will be first presented. The new technique to precisely place a hydraulic fracture in an openhole horizontal well drilled in any direction relative to the in-situ stress field is presented. The new technique is based on rock mechanics understanding of an openhole horizontal well under a given insitu stress field; thus it accounts for the near wellbore stress field to ensure creating a planar hydraulic fracture. Additionally, the new technique does not require costly mechanical isolation to place a hydraulic fracture. Basically, the new technique aims to bypass the near wellbore stress field such that the fracture can be conveniently initiated independently of the stress direction.This new approach is validated using laboratory experiments which will be discussed in details. The experiments were performed on simulated wells casted in rock samples with dimensions of 6"x 6"x10". The samples were triaxially loaded simulating various arrangements of a given wellbore relative to the in-situ stress field. Then, the simulated wells were hydraulically fractured using water based gel. Fracturing pressure versus time was recorded and analyzed.The experiments were very successful in proving the new concept to fracture openhole horizontal wells. The developed technique is fairly easy to implement and the impact of precise placement of a hydraulic fracture across an openhole horizontal well is illustrated.

The application of hydrajet technique to stimulate highly-deviated andhorizontal wells has become a successful method to improve well productivityfor different field conditions in the world. In the past 2 years, an operator company has successfully implemented arelatively new hydrajet stimulation technique in shallow waters off Brazil. Indeepwater locations, additional problems had to be overcome, which provedachievable using this new technology. This paper discusses a reservoir-based methodology to determine the optimumnumber of transversal fractures for a horizontal deepwater well. The methodstarts with the review of geology and stratigraphic aspects of the field tobetter understand the relationship between fracture orientation, geologicalfaults, and regional tectonic effects. With this preliminary characterization, well-log interpretation of the pilotwell and horizontal wellbore is performed to identify porosity and permeabilityindex of the carbonate formation being drilled. A study using well testing and nodal analysis is conducted to verifyreservoir properties based on real production data. Next, a numerical simulatoris used to obtain a production forecast varying the number of transversefractures intersecting the well. Finally an economic evaluation of net presentvalue vs. number of fractures is performed to determine the optimum number oftransversal fractures. Production results are then evaluated and compared to the other stimulationattempts in offshore horizontal completions in the area. Introduction In the complex world of hydrocarbon exploration and production, expectationsfor a certain level of economic success are not easily achieved. Obviously, there have been a few attempts rewarded with unexpectedly lucrative results.Unfortunately, this situation has become exceedingly scarce because ofever-depleting supplies in the world's known hydrocarbon-bearing formations.For obvious reasons, such cases will not be discussed in this paper. During the early years of oil exploration in Brazil, wells were drilled andcompleted as vertical wells. As the conducting surface in such wells weregenerally small (defined by p × diameter × formation height), production ratewas generally limited. Since well stimulation began in the early 1930s1 andeven more so after the present style hydraulic stimulation was invented in1949,2 most vertical wells have been stimulated at least once during the lifeof the well. Stimulation results are generally acceptable, although manytreatments did not produceeconomical results. In most cases, stimulationgenerally involves pressurization of the whole wellbore; with only a fewneeding isolation around the producing formation. As formations continue to deplete, treatment methods advance equally.Completion methods continue to advance, and the industry embarks upon adifferent approach: completing wells horizontally. These horizontal wells wereinitially completed openhole, and later were often completed with cementedcasing or uncemented preperforated liners to improve well integrity. Proponentssaid these wells, especially when completed openhole, would not require theconventional fracture stimulation, and reduce cost. Unfortunately, as alsooften experienced in vertical wells, operators in Brazil found many of theirhorizontal wells were under-achieving and therefore required stimulation.

Though fractures caused by stimulation will likely propagate away from high-permeability areas, the stimulation often provides a significant production improvement because of the large flow-path increase created by the fracture. This fact can be hard for many to accept. Placing two fractures consecutively in close proximity to each other may offer a tremendous benefit. With this approach, the first fracture is placed conventionally into the maximum stress direction. After a short delay, the second fracture is then placed, taking advantage of the temporary stress modification caused by the opening of the first fracture. This delay is computed so the stress modification at the tip of the second fracture is always maximized. This is done so that the second fracture will extend into the original (natural) minimum stress direction, meaning the fracture will extend into highly permeable areas and, therefore, production expectations from the second fracture will potentially be much larger than production of the first fracture. This leads to a significant increase in the revenue-to-cost ratio. In other words, a significant revenue increase can be achieved with an incremental cost increase. This new approach uses conventional pin-point stimulation methods; therefore, even though it is "new," it carries a very minimal risk with a potentially large payout. This paper discusses how the new process can be effectively performed by harnessing a pseudo-Maxwell/Kelvin-Voigt, creep phenomenon that is normally present in rock. The paper will also examine formation geology, reservoir aspects, best practices, better completion schemes, simulation data, and different stimulation and perforating techniques that would be best used for achieving maximum productivity. Introduction Since well stimulation was invented in the early 1930s, it has been understood that the primary intent is to improve communication from the formation to the wellbore by creating pathways from the formation rock to the well. At that time, rubbling was then the method of choice, primarily done by using TNT explosives (Ranney 1939). Acid has also been used. While both approaches have been shown to increase production, the effects are generally limited because they affect only areas within a short distance from the wellbore. Also, rubbling often causes wellbore collapse. Stimulation using formation fracturing techniques started in 1948 when a team from Stanolind Oil and Gas Co. placed a fracture in the rock by hydraulic pressurization (Hassebroek and Watters 1964). This has been an attractive approach until now because has proven to give longer-lived productivity increases. Mathematical modeling done throughout the years confirms that fractures provide a much larger surface to allow better communication from the formation to the wellbore (Economides et al. 1998; Wahl 1965; Vincent 2002). The Heterogeneous Reservoir Almost all reservoirs are heterogeneous, even though the level of heterogeneity may change from one location to another. Obviously, areas with high-level tectonic activity are very heterogeneous. On the other hand, flat, depositionally-formed formations are more homogeneous. In the area of stimulation, heterogeneity can have two meanings:a defined fracture direction within an area andan irregular "apparent" permeability pattern within an area. Until recently, a defined fracture direction meant that fractures created by stimulation would always follow a predefined stress within the area. It is also commonly believed that within a region, stresses are fixed; therefore fractures will always be parallel, all extending into the predefined direction. Hence fracture directions are regionalized and fixed, and should only be affected by the structure of the formation.

This paper reviews a unique, relatively new stimulation process that uses dynamic fluid energy (instead of mechanical methods) to isolate treatment fluid flow to a specific fracture point along the wellbore. A process of hydrajet-fracturing has been developed by merging four existing technologies: hydrajetting, hydraulic fracturing, jet pump technology, and dual-path fluid injection. These have been meshed to create a method whereby a wellbore is perforated (if necessary) and a fracture is initiated and placed accurately at a specific location, and then soon repeated at another chosen location uphole, or closer to the heel when in a lateral wellbore. The process was later expanded as a hydrojet-squeeze stimulation method also, even to the point of applying both of these applications while stimulating a single wellbore. This process employs two independent fluid streams: one in the treating string and another in the annulus. As these fluid paths will be supplied with separate pumping equipment, we have the option to instantaneously alter the downhole mixture that is being used to treat the formation at the current location of the jetting tool. An additional use of this two-stream feature is the capability to pump two different fluids that can be mixed downhole with a tremendously high energy to form a homogenous mixture at the fracture entry point, even creating foamed fluids insitu for some applications. This technique has been used to stimulate more than 50 horizontal or highly deviated wells (and a few vertical wells) as of the preparation of this paper, both proppant-laden fractures and fracture acidizing treatments. On average, more than 7 fractures were placed along a typical horizontal wellbore, typically several hundred feet apart without the use of mechanical sealing equipment. Additionally, numerous horizontal wells with higher permeabilities have been stimulated using the hydrajet-squeeze process alone. The diversion process follows a dynamic isolation approach that uses a high-velocity, high-energy jetted fluid. The process was originally developed for its unique stimulation capabilities in openhole horizontal wells, but has been extended to wells that have cemented or non-cemented liners, whether vertical, deviated, or horizontal and even to multilateral completions (or recompletions). This paper offers insight into many of these treatments, including the different well situations, design considerations, operations, and available results of the treatments. Possible unconventional approaches using this concept and a unique implementation in the field are also discussed. Introduction When an operator considers a horizontal completion in a low-permeability carbonate or sandstone reservoir, cost containment becomes a prime drilling and completion consideration. For many recent and currently planned projects throughout the world, the opportunity for openhole horizontals to give increased production per completion dollar economically may be what justifies the development of a new field or additional drilling in an existing field. Also, the re-entry of older vertical wells for horizontal recompletions may dictate that the completion is openhole because of hole-size limitations. The global reality that our industry seems slow to accept is that horizontal completions in low-permeability reservoirs usually require significant stimulation for achieving truly economic production rates. Many horizontal-drilling programs have been based on often incorrect assumptionsthat long openhole laterals will avoid the need for expensive stimulation treatments normally required for economic vertical-well completions in that reservoir. Hydrojetting, the use of water under high pressure, is a well known technique that many industries use to perform different tasks.1 These tasks include cleaning and preparing surfaces, placing cements, drilling, cutting, slotting, perforating, machining, grouting, mining, and even household uses such as car washing and dental hygiene. Sand-laden fluids can be used, or cavitating jets may be required. Jetting pressures have ranged from a few hundred psi to 60,000 psi.