Placing Two Fractures Consecutively in Close Proximity to Significantly Increase Revenue-to-Cost Ratio

Abstract

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.

Efficient Coiled-Tubing Fracturing for Proppant-Placement Assurance and Contingency-Cost Mitigation

“…Using this type of system, windows can be opened or closed in any sequence as prescribed. The process takes advantage of two phenomena: the altered stresses that can occur when a nearby fracture is opened (Warpinski et al 1989, Surjaatmadja 2007a, 2007b, 2007c2008;Moschovidis et al 2000) and the creation of slip planes by the naturally varying widths of each fracture forming the horizontal microfractures, as illustrated in Fig. 7 (Surjaatmadja 2010).…”

A Novel Hydraulic Fracturing Technique Greatly Improves Hydrocarbon Recovery Through the Use of Temporary Beneficial Changes in Stress Anisotropy

“…As such, formations were generally near the surface. It was quite common for hydrocarbons to be discovered at depths less than 4,000 ft, and performing simple fracture stimulations was usually sufficient to obtain acceptable production (Surjaatmadja 2007a(Surjaatmadja , 2007b(Surjaatmadja , 2007c(Surjaatmadja , 2008(Surjaatmadja , 2010Lewis and Surjaatmadja 2015). However, as shallow formations became less productive and deeper formations were explored, finding new producing areas in a known producing formation could be described as Љhit and missЉ (Surjaatmadja et al 2003), meaning that luck was often a factor.…”

“…Assuming the channels shown in Fig. 1 are permeable streaks, the fracture will follow the local maximum stress direction, which will not intersect the permeable feature (Surjaatmadja 2008;Lewis and Surjaatmadja 2015). Therefore, the ability to temporarily modify this local maximum is important.…”

“…Note that, considering the cost outlay (including time lost, equipment, etc.) of the second fracture is small compared to the first fracture alone, this second fracture placement is obviously quite desirable (Surjaatmadja 2007c(Surjaatmadja , 2008. Therefore, the primary interest of this investigation was to perform a drastic modification of the anisotropy landscape by placing a first fracture, causing a motion of the fracture face into the direction of the permeable feature, thus temporarily causing the rock to be compressed temporarily.…”

“…Surjaatmadja suggests that the missing factor in these studies was time (Surjaatmadja 2007a(Surjaatmadja , 2007b(Surjaatmadja , 2007c(Surjaatmadja , 2008) (e.g., the dynamics of the rock movement process). He argues that the behavior of formation rock can be conveniently modeled as a Couette interaction between rock layers (or, in Couette's terms, Љflow linesЉ); hence, the behavior of the rock during a fracture opening process can be represented by a very viscous media, such as plastic models.…”