Hydraulic fracturing continues to be the primary mechanism to produce hydrocarbons out of unconventional reservoirs like tight gas sands, tight coals and shale reservoirs. Over the last few decades it has been studied extensively. However, all the issues that arise during a stimulation treatment have not been understood correctly, yet, leading to costly trial and error approaches to fix them. Assuming that a majority of the perforations (or sleeves) are open and there are no issues with the stimulation fluids, screen-outs and/or pressure-outs during stimulation treatments in any type of reservoir can be attributed to either high pressure-dependent leakoff (PDL) or high process-zone stress (PZS). With high PDL the end result will be a screen-out if it is not addressed properly. However, with high PZS, it is the first indicator and in conjunction with fracture gradient and local stress environment one can understand the reasons for pressure-outs or screen-outs. With high PZS pressure-outs are more common than screen-outs. The objective of this work is to clearly explain and quantify these reservoir-related issues and once identified present solutions such that screen-outs and pressure-outs can be avoided in refracture and new well treatments. The effect of damage zone and the fluid lag or negative net stress zones and their contribution to the fracture tip effects will be presented. This work will also clearly show that zones that exhibit high PZS (greater than 0.20 psi/ft), irrespective of the formation type, are economically poor producers.The tools for identifying these reservoir-related parameters include a diagnostic fracture-injection test (DFIT) and a grid-oriented fully functional 3D fracture simulator with shear decoupling. The relationship between high PZS and the local stress environments and their contribution to issues during a stimulation treatment are presented based on the analysis of 3000 plus DFIT's from the Rockies. Coal, tight gas sand and shale formations are part of the 3000 plus DFIT dataset presented in this work. Examples from coal and shale formations presented earlier by the author are referred in this work. Finally, guidelines (Ramurthy 2012) are presented such that stimulation treatments in high PZS zones that contribute to poor production can be avoided and high PDL zones that lead to good production can be optimized, thereby saving completion costs.
Effective and economic recovery of oil from fractured reservoirs by steamflooding rely on thorough understanding of the physical process mechanisms. The objective of this research is to study steamflooding mechanisms in fractured porous media using laboratory experiments and mathematical modeling. The experimental results have been published previously [1-3]. A mathematical model developed for simulating laboratory coreflood results is presented in this paper. The model is a two-dimensional, three phase, thermal simulator which includes the effects of gravity, capillarity and thermal swelling. Thermal effects on capillary pressure and relative permeabilities are included. Simulation and analysis of laboratory experiments are presented. Sensitivity studies demonstrate the effects of injection rate, pressure and temperature, fracture aperture, capillary pressure, and relative and absolute permeabilities on oil production.
Coalbed methane has emerged as a significant resource for natural gas production in the United States, with estimates of gas-in-place of 400 trillion cubic feet. In Wyoming the largest coalbed methane resources occur in the Greater Green River, Powder River, and Wind River Basins. Very little of this gas has been exploited. This paper examines the potential of coalbed methane production in the Powder River basin by history matching early production from five gas wells in the Rawhide Butte field using a commercially available coalbed methane simulator, COALGAS. Sensitivity studies showed the most important parameters for establishing production were permeability, initial desorption pressure and drainage area. Langmuir constants, desorption time, porosity, well-bore diameter and skin were comparatively less important for long term production. An economic analysis showed that, based on current capital and operating costs obtained from industrial companies, the development of coalbed methane in the Powder River Basin may be economic if the gas sales price is greater than approximately $1/Mscf.
Engineering educational institutions have a dominant role to play in shaping the future course of energy and mineral industries. When researching and defining the needs for educating engineers for the next century, Gentry (1) has concluded, "we must develop and implement educational experiences, both in the classroom and the research laboratory, that enable students to keep pace with the world and the technological, social, political, and economic initiatives that drive it." In its "University-Industry-Government (UIG) Partnership for Quality Engineering Personnel" program announcement (2) the National Science Foundation noted three major impediments to maximizing the quality of engineers produced by some of our academic institutions. "One of them being failure to incorporate major elements of engineering practice into engineering curricula". Apparently the incorporation of such a factor in classrooms has been a matter of high importance in the NSF Engineering Infrastructure Development Program office recently. This paper addresses and investigates some of the aspects of such a practice from teaching principles as well as methodology points of view. There are many ways one can define "Teaching" and still not be satisfied with the completeness and certainty of these definitions. The reason lies in the fact that the process of teaching involves art, science and humans. Madeline Hunter (3) tries to explain nature of teaching very succintly: "Educators have finally arrived at the point that professionals in medicine achieved when the latter discovered that germs and not evil spirits were causing much of the problem. We now know many cause-effect relationships in teaching and learning. As a result, we can use those causal relationships to promote student learning in the same way the doctor uses his medical knowledge to promote health. In both education and medicine we are learning more each day even though there still remains much we don't know."
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.