The Important Second Fracture and Its Optimal Placement for Maximizing Production

Day 2 Wed, February 26, 2014

Coffman

et al. 2014

Self Cite

In the oil field, rock testing (beyond standard core analyses) is generally limited to three classes-flow tests to determine the production characteristics of the rock in question, chemical tests to determine reactivity of the rocks, and testing the mechanical qualities of the rock to determine the resistance of the rock to forceful intrusions, such as drilling, perforating, and stimulations. Tests to determine mechanical qualities are mostly limited to static or steady state conditions; for example, Young's moduli and Poisson's ratio measurements, compressive strengths, tensile strengths, or anything that offers easily understood and useful data.This paper discusses the creation of a new test process in which time is used as an aspect of the rock mechanics science in the oil field. For example, a question such as "how much pressure is required to fracture the rock" is henceforth replaced by a question such as "how long does it take for the rock face to move from point 'A' to point 'B'?" To do so, rock testing facilities must be reformulated to include accurate motion monitors and sound detection for live capturing of events within the rock at accurate time steps, such as microseisms, etc. The paper also discusses the use of this technology to plan and create different methods of fracture stimulating a formation; in particular, creating multidirectional fractures to maximize well production is discussed.

Section: Anisotropy Modification At Workmentioning

confidence: 96%

Section: Anisotropy Modification At Workmentioning

confidence: 99%

New Dynamic Rock Test System to Assist in Planning and Creating Multidirectional Fractures

Looper

Day 2 Wed, February 26, 2014

Coffman

et al. 2014

Self Cite

The Mythical Second Fracture and Its Optimal Placement for Maximizing Production

2007

All Days

Placing a fracture in a formation is obviously well understood in our industry and has been practiced successfully for quite some time. Recently this capability was refined to enable initiation of a fracture into a specific direction through the introduction of super-high-energy jetting. Despite the developments and experience in fracturing technology and know-how, it has still not been possible to know where a far-field fracture goes---we know it will go to the local minimum stress direction---but we do not know what direction that will be. It is most probable that the far-field fracture will go to a less-than-desired area in the formation and result in only an "acceptable" improvement in production. Recently, it has been shown that refracturing actually creates new fractures in the formation, rather than simply reopening old fractures, as was commonly thought. Even reopened fractures are now known to result in new areas being reached by the fractures. It is the opinion of this paper that these new fractured areas are not substantially different from the areas reached by the first fracture because local depletion enhances the effects of the original stress regime. This paper discusses the generation of multiple, consecutive fractures created in a way that enables them to reach formations in a manner not reached before using conventional means. In this scheme, the first fracture achieves "acceptable" production goals. If the process stopped at that point, the expense for this "mediocre" production increase would be high. However, in the new process, a second fracture is quickly initiated to take advantage of the stress modification created from the first fracture, allowing the second fracture to reach more productive rock not accessible to the first fracture. This paper will present field data that supports the feasibility of this concept. Various situations where this approach could reap substantial benefits are also presented. Introduction Fracture stimulation has become an art mastered by many frac engineers worldwide. Nevertheless, mysteries about mother earth still prevail, leading to unending surprises in the behavior of formations and continually challenging scientists and engineers. As fracturing theories develop, several questions remain unanswered; for example: Where exactly does the fracture go? and, What is the precise shape and measurement of the fracture? The fact is, due to the lack of homogeneity of formations, precise solutions cannot exist. Nevertheless, this fact should not discourage anyone from attempting to find the closest, best solution. It is generally agreed that accurate shape and size of a fracture are probably not as important as determination of its true direction and reach into the reservoir. Furthermore, important information for the engineer relating to fracture reach would include whether or not a fracture will extend into a water zone or gas cap. This paper is directed toward finding ways to predict fracture direction within a specific formation and using the knowledge to create better, more effective fractures. In the literature on this subject, many (including the author) have attempted to determine true fracture direction through the use of accurate measuring devices, experiences, and even geological data.1–4 It is this author's belief that understanding the geological activities of a formation can provide the best prediction of fracture direction. Geological knowledge combined with knowledge about formation pressures could be used to determine fracture direction more accurately. However, it is not the intent of this paper to apply knowledge about natural fractures to "predict" fracture direction and behavior for man-made fractures in the same formation. Rather, the primary purpose of this paper is to utilize knowledge about man-made fracturing and refracturing to adapt a means to create fractures in the future that will more effectively improve production for a given formation.

Single Point of Initiation, Dual-Fracture Placement for Maximizing Well Production

European Formation Damage Conference

2007

Self Cite

fax 01-972-952-9435. AbstractPlacement of a fracture in a formation has become a wellunderstood process in the industry. Recently, this practice was improved by the introduction of a method to properly initiate the fracture into a specific direction using super-high-energy jetting. A drawback of this jetting method though is not knowing exactly where the far-field fracture has gone. Although we know that the fracture will extend in the local minimum-stress direction, it is not known where that direction might be. In all probability, the fracture has gone into a lessthan-desired area in the formation, and will result in only an "acceptable" improvement of production.It was once thought that refracturing merely reopened existing fractures. Recently, however, it has been shown that refracturing can actually create new fractures. In addition, when refracturing causes older fractures to reopen, the results generally show that some new area has been reached by the fracture. It is the opinion of this paper that these new areas are not substantially different from the one reached by the first fracture because local depletion enhances the effects of the original stress regime. This paper discusses a process whereby fractures are generated in a formation using at least two different fracturing techniques to reach formations in a manner not reached by conventional fracturing alone. In this process, the first fracture may achieve "acceptable" production goals, although the cost may be high. A second fracture is then quickly created to take advantage of the stress modification resulting from the first fracture. This rapid followup fracture is thus able to reach more productive rock not accessible to the initial fracture. Field data supporting the feasibility of this concept will be presented. Various situations where this approach could reap substantial benefits are also described.