As a long time JCPT reader, I would like to take this opportunity to wish you a very happy, productive, and prosperous new year in 2015. Thank you very much for your continued support and involvement. It has been and will remain to be of vital importance for JCPT. As it is for all other peer-reviewed SPE journals, the main objective of JCPT is to bring you technologies you can use and solutions you can trust. JCPT offers a unique platform for high-quality technical communications and exchanges covering all aspects of technologies involved in upstream challenges in the Canadian petroleum industry. In order to maintain this advantage, your feedback is strongly encouraged. Please send your comments, either technical or editorial, and any discussions on papers published in JCPT to firstname.lastname@example.org. For more details, please visit: http://spe.org/publications/journals.php.
In this issue, all three papers deal with fundamental questions. Observations from the field often require diagnostic analysis that logically connects them together with the knowledge we already possess. New understanding, and occasionally new discoveries, could arrive as the result of such analysis. In doing so, laboratory tests, theoretical and numerical modelling, etc. often play critical roles.
Thermally induced deformation of shale can have nontrivial impacts on the performance of thermal recovery processes. It is known from laboratory tests that shale can expand as well as contract under thermal conditions. What are the physics behind the thermally induced deformation behaviour in shale? What are the key parameters that govern this behaviour? Instead of relying on phenomenological or empirical approaches, Li and Wong, in their paper entitled Effect of Heating in Steam-Based-Oil-Recovery Process on Deformation of Shale: Compositional Thermal Strain Model, attempt to establish a compositional thermal strain-modelling approach on the basis of fabric for answering these questions. They concluded that clay fraction can be a key parameter.
In the second paper, A Fractal Model for the Stress-Dependent Permeability and Relative Permeability in Tight Sandstones, Lei et al. attempt to establish a theoretical model investigating the impacts of confining or effective stress on permeability and relative permeabilities of tight sandstones. This subject is not new. Laboratory tests have shown noticeable variations of permeability and relative permeabilities in porous media under stress. However, these behaviours are not well understood, although modelling has been attempted. Having recognized the fractal characters of the pore space in porous media in the nature, authors derived a new model for normalized porosity, permeability, and two-phase noncompressible relative permeabilities in sandstones under effective stress using the fractal concept. To most of our readers with strong traditional background, this approach could be observed as counter-intuitive and even controversial. However, it could also be a small, yet significant stepping stone for the path toward a better understanding of some of the natural phenomena relevant to our industry, such as the one this paper is trying to tackle.
The third paper entitled Prevention of Acid-Induced Asphaltene Precipitation: A Comparison of Anionic Vs. Cationic Surfactants by O’Neil et al. deals with a fundamental and practical issue in operation—the tendency of asphaltene precipitation in acidic environment, along with the tendency of emulsification in the common prevention practice by blending with surfactants. Targeting Beaverhill Lake Formation, this paper reports a comprehensive study, including laboratory tests, theoretical considerations, field tests, and cost comparisons for determining niche strategies of using antisludge agents.
I hope these papers not only are enjoyable to read, but also stimulate your thoughts and encourage you to share your opinions and perspectives with other fellow readers through JCPT.
Dr. Jian-Yang (JY) Yuan, BSc, MSc, PhD
Dr. Jian-Yang (JY) Yuan is Principal EOR Advisor at Osum Oil Sands Corporation. Previously, he worked with Canadian Natural Resources as an exploitation specialist and with Alberta Research Council as a steam-assisted gravity drainage strategic area leader. Yuan started his career in heavy oil and the oil-sands industry with Imperial Oil Resources as a Natural Sciences and Engineering Research Council of Canada Industrial Fellow in 1993. He holds a BSc degree (with honours) in nuclear physics from Nanjing University and MSc and PhD degrees in theoretical physics from the University of Maryland. Yuan is currently an active member of SPE and the Canadian Heavy Oil Association.
Effect of Heating in Steam-Based-Oil-Recovery Process on Deformation of Shale: Compositional Thermal Strain Model presents a new thermal strain model to quantify the thermally induced deformation in shallowly buried shales. The microfabric and the clay-bound water are considered in the new model. The effect of clay fraction and the imposed temperature on the contraction or expansion behaviour of shales are highlighted. The model is validated against the laboratory test result of a shale sample retrieved from a heavy-oil field in the western Canada sedimentary basin. Discussions on the stress and drainage conditions on thermal strain behaviour, anisotropy in thermal strain, and the model’s practical application in thermal recovery of heavy oil are outlined.
A Fractal Model for the Stress-Dependent Permeability and Relative Permeability in Tight Sandstones discusses the successful derivation validation and analysis of a new mathematical model for normalized porosity, normalized permeability, and two-phase relative permeability in tight sandstone porous media under effective stress. A description of the correlations for stress-dependent permeability obtained in a previously published paper is outlined. Former studies of stress-dependent relative permeability are summarized. A new method, which can find the stress-dependent permeability and relative permeability of the tight porous media analytically, is highlighted. Results discuss selection, model validation (the stress-dependent irreducible water saturation, the stress-dependent permeability, and stress-dependent relative permeability), and parameters’ sensitivity analysis in detail.
Prevention of Acid-Induced Asphaltene Precipitation: A Comparison of Anionic Vs. Cationic Surfactants looks at different types of antisludging agents and how they impact the effectiveness of an acid treatment. Progressive development of acid-fracturing treatments in the Beaverhill Lake formation has led to a significant increase in the size of the treatments and an increase in the strength of hydrochloric acid used. With these changes, the potential of causing damage during the acid treatment becomes even more critical. The Beaverhill Lake formation is especially prone to formation damage by asphaltene precipitation as a result of contact between the oil and strong acids. There are several chemistries to prevent these damage mechanisms and the mechanism of these chemistries on the asphaltene molecule is discussed. In addition to these mechanisms, laboratory testing and a case study will be reviewed to show the effects that these additives have on the oil, the formation, and ultimately how each of these chemistries effect the production of the wells.