In recent years, new fracturing designs and techniques have been developed to enhance production of trapped hydrocarbons. The new techniques focus on reducing stress contrast during fracture propagation while enhancing far field complexity and maximizing the stimulated reservoir volume. Zipper frac is one of these techniques, which involves simultaneous stimulation of two parallel horizontal wells from toe to heel. In this technique, created fractures in each cluster propagate toward each other so that the induced stresses near the tips force fracture propagation to a direction perpendicular to the main fracture. The effectiveness of zipper frac has been approved by the industry; however, the treatment's optimization is still under discussion. In this paper, we present a new design to optimize fracturing of two laterals from both rock mechanic and fluid production aspects. The new design is a modification to zipper frac, where fractures are initiated in a staggered pattern. The effect of well spacing on the changes in normal stress has been evaluated analytically to optimize the design. Results demonstrate that the modified zipper frac improves the performance of fracturing treatment when compared to the original zipper frac by means of increasing contact area and eventually enhancing fluid production.
The role of geomechanics in design and evaluation of hydraulic fracture stimulations in unconventional reservoirs has become more important than ever. Microcosmic mapping provides a good estimation of fracture geometry and stimulated reservoir volume (SRV); however, without geomechanical considerations, the predictions may not be completely accurate. By understanding reservoir rock mechanics and those parameters that have a major impact on the performance of fracture treatments, more reliable decisions in fracturing design and optimization can be made. This paper presents the results of an analytical model that predicts the changes in stress anisotropy in the neighborhood of the fractures of different designs in an elastic-static medium. Also, a numerical model has been used to investigate the effect of different geomechanical parameters on the geometry of the fractures. Results show that the spacing between fractures has a major impact on the changes in stresses. The effect of well spacing on fracture geometry in modified zipper frac design has been investigated. The results of this study give valuable insight into optimization of fracture placement in newly developed designs of hydraulic fractures in horizontal wellbores.
Real-time analysis of fracturing data is an invaluable tool for determining whether a fracturing job is progressing as planned. Since early days, understanding of fracturing pressure was emphasized and practiced by the industry. The most well-known fracturing-pressure-analysis tool is the Nolte-Smith technique. To predict the geometry of a hydraulically induced fracture, the Nolte-Smith technique analyzes the pressure response of a formation during pumping. Extensive application of this technique has proved reliable to interpret fracturing events. However, the compression of data imposed by logarithmic scale may make the detection of some events difficult. In addition, the Nolte-Smith technique necessitates prior accurate knowledge of formation-closure pressure.In this paper, we present a real-time fracturing diagnostic. This method, which is based on a modification of the Nolte-Smith technique, has proved reliable in the interpretation of fracturing behavior while a fracturing job is being carried out. In addition, it eliminates the shortcomings of the original technique, meaning that while making the interpretation of fracturing pressure faster, the new technique does not require prior knowledge of formation in-situ stresses. This technique was reached by a new innovative moving-reference-point concept assembled with the power-law fracture-propagation theory. Application of the new technique in the analysis of a variety of field cases, including several frac-pack and regular fracturing treatments, proved successful.
Excessive water production has been a problem in the oil industry for many years. To handle this problem, many research projects have focused on developing conformance control systems. Conformance fracturing, a combination of hydraulic fracturing and water control, has proven to be an effective conformance control technique. Hydraulic fracturing is now the technology of choice for increasing well productivity. The chemistry of relative permeability modifiers has also undergone extensive change; the most notable result of which has been to prolong the life of water control treatments using relative permeability modifier (RPM) polymers. The purpose of this study was to investigate the application of barrierfracturing using streamline simulation. Barrier-fracturing is a novel idea that involves modifying the flow profile and diverting the displacing fluid by placing a fracture with essentially zero permeability deep into the reservoir. There are many ways to create a zero permeability fracture, examples of which include injection of cement or a conformance fluid into the fracture. In our study, we created several streamline simulation models to show the fidelity and validity of this innovative idea. The streamline simulation models that are presented in this paper range from a simple homogeneous reservoir to a very heterogeneous reservoir. The effect of different barrier-fracture lengths on the reservoir performance was analyzed. We also built streamline models for conventional mechanical and chemical water shutoff techniques (e.g. re-completion and RPM) to compare them with the novel barrier-fracture water shutoff technique. The resulting saturation distribution maps from the longer barrier-fracture clearly show the power of a barrier-fracture to modify flow profile and divert the displacing fluid in comparison to conventional water shutoff techniques. Barrier-fractures helped improve oil recovery by delaying water-breakthrough and eventually improving the volumetric sweep efficiency.
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