Placing Two Fractures Consecutively In Close Proximity from Each Other to Significantly Increase Revenue to Cost Ratio
- Jim Basuki Surjaatmadja (Halliburton Energy Services Group)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 20-22 October, Perth, Australia
- Publication Date
- Document Type
- Conference Paper
- 2008. Society of Petroleum Engineers
- 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.6.4 Drillstem/Well Testing, 1.10 Drilling Equipment, 4.3.4 Scale, 2.4.3 Sand/Solids Control, 1.8 Formation Damage, 2 Well Completion, 4.1.5 Processing Equipment, 2.5.4 Multistage Fracturing, 2.2.2 Perforating, 3 Production and Well Operations
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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.
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: (1) a defined fracture direction within an area and (2) an 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.
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