Abstract. In electrical heating systems, the electrical power consumption should be lower than the Contracted Power Limit. Energy distribution devices are used to solve this problem, but they are only concerned with the electrical energy. We claim that this energy distribution must also consider the comfort level in the building. In this work, an electrical energy distribution MAS for coordinating the electrical heaters is proposed. The MAS is responsible for both objectives: the electrical power must be lower than the Contracted Power Limit and the comfort level in the building must be maintained if sufficient power is available. The MAS is now being implemented in a real world application of an electrical heating system marketed by a local company.
Identification of the correct cause of wellbore instability is the key to quickly solve the problem. This paper presents some results of tests conducted to check the behavior of preserved shale samples when immersed in different solutions, trying to identify the importance and relevance of the osmosis as well as the effect of other components in the mud, such as the emulsifier. Results showed that not only the salinity of the mud is important. Also, in some situations, rock swelling did not follow what states the osmosis theory, leading to a conclusion that other phenomena are relevant and with a similar order of importance. The paper also discusses the mechanism of micro-cracking with subsequent fluid penetration, and the use of a truly non-invasive fluid to avoid the instability. Field cases are reported, demonstrating the effectiveness of using such approach. The paper also presents the problems ofcurrent rig site monitoring tests that can induce wrong interpretation of the real cause of the problems. Introduction Along the last decades several approaches, ideas, and concepts have been derived from the various wellbore-instability related problems and from extensive laboratory investigation1. These old concepts were all attributed to strong shale-fluid interaction, with the fluid causing a severe detrimental effect on the integrity of the rock. In the beginning of the 90 s some of these concepts started to be questioned due to sample mishandling procedures in the laboratory. Several laboratory investigations were carried out in different institutions, with the aim of learning the actual behavior of downhole shales when in contact with different drilling fluids. Works recently published2–8 showed that not all shales present a strong reaction with water. Therefore, the old idea that most, if not all, shale instability problems are related to rock-fluid interaction might not be true. This paper addresses first the evolution and understanding of wellbore stability problems. Is not the intention to generate a complete review or to cover all the aspects, but to provide a thinking process on the different aspects that might be creating misunderstanding and leading to wrong decision in the field. On the same line some instability mechanisms are briefly described. The problems faced in the field are described, with some cases where wrong interpretation might have been the most probable cause of the instabilities. Traditional and old concepts used did not solve the problem. According to the traditional theories, the problems should not have happened by using the solutions employed. The paper finally points out what should be the best option in terms of properties for a drilling fluid in order to avoid the instability problems commonly encountered. This change in paradigm will demand a significant switch in the current products available, rig site tests, and fluid maintenance at the rig. Obviously this takes time, and only field evidences that can prove the new approach isd the appropriate one will accelerate the process. Wellbore Stability History Wellbore instability problems were historically attributed to strong interaction between the shale and water based drilling fluids. In order to minimize this problem oil-based muds have been developed, since shale does not interact with oil. However, even with the use of oil-based muds, which has a water phase dispersed in most of the situations, instability problems were still observed. In the 60's it was proposed a theory that shale would still absorb water from the oil-based drilling fluid, in case the salinity of the water phase was smaller than the salinity of the shale. This theory tried to explained the instability problems when using oil-based muds, still utilizing the idea of shale hydration due to water adsorption. It was then proposed that the water-phase should have a salinity, later evolved to activity compatible with the one of the shale, to avoid movement of water from the drilling fluid into the shale.
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.