Shale gas is becoming increasingly important globally. The nature of these reservoirs pose special considerations in reserves estimation. What follows was written in 2001 and needs to be updated based on current experience. Nonetheless, some of the considerations mentioned remain appropriate. As reported in mid-2000, natural gas produced from shale in the US has grown to be approximately 1.6% (0.3 Tcf annually) of total gas production.
The amount of trapped oil in hydrocarbon rich shale reservoirs recoverable through Enhanced Oil Recovery methods such as low salinity water flooding has been an ongoing investigation in the oil and gas industry. Reservoir shales typically have relatively lower amounts of swelling clays and in theory, can be exposed to a higher chemical potential difference between the native and injected fluid salinity before detrimental permeability reduction is experienced through the volumetric expansion of swelling clays. This fluid flux into the pore spaces of the rock matrix acting as a semi permeable membrane is significant enough to promote additional recovery from the extremely low permeability rock. The main goal of this paper is to determine how osmosis pressure build up within the matrix affects geomechanical behavior and hydrocarbon fluid flow. In this study we investigate Pierre shale samples with trace amount of organic content and high clay content as an initial step to fully understanding how the presence of organic content affects the membrane efficiency for EOR applications in shales using low salinity fluid injection. The same concept is also valid when slickwater is utilized as fracturing fluid as majority of the shale reservoirs contain very high salinity native reservoir fluid that will create large salinity contrast to the injected slickwater salinity.
The organic-rich reservoir shales typically have a TOC content of approximately 5 wt% or higher with TOC occupying part of the bulk matrix otherwise to be filled up by clays and other minerals. With less clay within the rock structure, the amount of associated clay swelling arising from rock fluid interaction will be limited. The overall drive of water into the matrix brings added stress to the pore fluid known as osmotic pressure acting on the matrix that also creates an imbalance in the stress state. The native formation fluid with salinity of 60,000 ppm NaCl has been used while 1,000 ppm NaCl brine is utilized to simulate the low salinity injection fluid under triaxial stress conditions in this phase of the study reported here. A strong correlation is obtained between the osmotic efficiency and effective stress exerted on the shale formation. The triaxial tests conducted in pursuit of simulating stress alteration under the osmotic pressure conditions and elevated pore pressure penetration tests indicated that the occurrence of swelling directly impact the formation permeability. These structural changes observed in our experimental results are comparable to field case studies.
Gas production from shale formations is growing, especially in the USA. However, the origin of shale gases remains poorly understood. The objective of this study is to interpret the origin of shale gases from around the world using recently revised gas genetic diagrams. We collected a large dataset of gas samples recovered from shale formations around the world and interpreted the origin of shale gases using recently revised gas genetic diagrams. The dataset includes >2000 gas samples from the USA, China, Canada, Saudi Arabia, Australia, Sweden, Poland, Argentina, United Kingdom and France. Both free gases collected at wellheads and desorbed gases from cores are included in the dataset. Shale gas samples come from >34 sedimentary basins and >65 different shale formations (plays) ranging in age from Proterozoic (Kyalla and Velkerri Formations, Australia) to Miocene (Monterey Formation, USA). The original data were presented in >80 publications and reports. We plotted molecular and isotopic properties of shale gases on the revised genetic diagrams and determined the origin of shale gases. Based on the distribution of shale gases within the genetic diagram of δ13C of methane (C1) versus C1/(C2+C3), most shale gases appear to have thermogenic origin. The majority of these thermogenic gases are late-mature (e.g., Marcellus Formation, USA and Wufeng-Longmaxi Formation, China) and mid-mature (associated with oil generation, e.g., Eagle Ford Formation, USA). Importantly, shales may contain early-mature thermogenic gases rarely found in conventional accumulations (e.g., T⊘yen Formation, Sweden and Colorado Formation, Canada). Some shale gases have secondary microbial origin, i.e., they originated from anaerobic biodegradation of oils. For example, gases from New Albany Formation and Antrim Formation (USA) have secondary microbial origin. Relatively few shale gases have primary microbial origin, and they often have some minor admixture of thermogenic gas (e.g., Nicolet Formation, Canada and Alum Formation, Sweden). Two other revised gas genetic plots based on δ2H and δ13C of methane and δ13C of CO2 support and enhance the above interpretation. Although shales that contain secondary microbial gas can be productive (e.g., New Albany Formation, USA), the resource-rich, highly productive and commercially successful shale plays contain thermogenic gas. Plays with late-mature thermogenic gas (e.g., Marcellus Formation, USA and Wufeng-Longmaxi Formation, China) appear to be most productive.
The session will cover an area of growing interest, given increasing concern about wellbore integrity and well control. As with other MPD systems, SMD technology offers early detection of influxes (kicks) and minimizes downhole losses to weak subsurface formations. This paper describes a number of system enhancements, including the ability to display and analyze not only the critical parameters of drilling hydraulics but also other information that allows different perspectives in considering the closed-loop system. The paper demonstrates the successful application of advanced automated managed-pressure-drilling (MPD) technologies on the Dover well close to Fort McMurray, Alberta, Canada. The development of the Kanowit field offshore Sarawak, Malaysia, requires the drilling of two subsea development wells with a semisubmersible rig.
The contract is helping to solidify Europe’s offshore sector as the focal point for the rise of automated drilling technology. This paper presents a case history of drilling automation system pilot deployment, including the use of wired drillpipe, on an Arctic drilling operation. In this paper, the application of a real-time T&D model is demonstrated. The process of T&D analysis was automated, and the time and cost required to run physical models offline was reduced or, in some cases, eliminated. The latest example of the offshore sector's march toward automated wellbore construction will take shape later this year in the North Sea.
Showing concern for the high emission of green house gases, the governments all over the world are coming up with more stringent rules to check the emission level. Steam Assisted Gravity Drainage is a highly energy intensive process where huge amount of steam is generated by heating natural gas or coal thereby generating a very large share of green house gases. Therefore, solar energy seems to be lucrative in the following ways: world areas with abundant solar irradiation level can be tapped to reduce the fossil fuel consumption, minimizing the cost spent on fossil fuel and the emissions level at the same time. Concentrated Solar Power (CSP) looks a very promising technique but it comes with its own limitations mainly due to the requirement for huge area for setting up the solar collectors. Water Soluble Carbon-N115 is a sub-micrometer particle that has size less than the wavelength of light. Due to this reason, instead of scattering light, it absorbs light. The nano-particle gets enveloped in a thin layer of steam when put in a water bath. The vapour is released after reaching liquid-air interface and the nano-particles revert back to the solution to repeat the vaporization process and they exchange heat with the fluid, slightly raising the fluid temperature resulting in boiling of the fluid volume as a parallel effect. The paper discusses a model incorporating this nano-particle for the reduction of solar field footprint by more than a quarter and thereby reducing the cost and operational area. The paper also suggests the places across the globe where the proposed method can be deployed for generating steam and ultimately injecting it for producing oil above the surface from a tar-sand reservoir.
Xiong, Hao (University of Oklahoma) | Huang, Shijun (China University of Petroleum, Beijing) | Devegowda, Deepak (University of Oklahoma) | Liu, Hao (China University of Petroleum, Beijing) | Li, Hao (University of Oklahoma) | Padgett, Zack (Univiersity of Oklahoma)
Hao Xiong, University of Oklahoma; Shijun Huang, China University of Petroleum, Beijing; Deepak Devegowda, University of Oklahoma; Hao Liu, China University of Petroleum, Beijing; and Hao Li and Zack Padgett, University of Oklahoma Summary Steam-assisted gravity drainage (SAGD) is the most-effective thermal recovery method to exploit oil sand. The driving force of gravity is generally acknowledged as the most-significant driving mechanism in the SAGD process. However, an increasing number of field cases have shown that pressure difference might play an important role in the process. The objective of this paper is to simulate the effects of injector/producer-pressure difference on steam-chamber evolution and SAGD production performance. A series of 2D numerical simulations was conducted using the MacKay River and Dover reservoirs in western Canada to investigate the influence of pressure difference on SAGD recovery. Meanwhile, the effects of pressure difference on oil-production rate, stable production time, and steam-chamber development were studied in detail. Moreover, by combining Darcy's law and heat conduction along with a mass balance in the reservoir, a modified mathematical model considering the effects of pressure difference is established to predict the SAGD production performance. Finally, the proposed model is validated by comparing calculated cumulative oil production and oil-production rate with the results from numerical and experimental simulations. The results indicate that the oil production first increases rapidly and then slows down when a certain pressure difference is reached. However, at the expansion stage, lower pressure difference can achieve the same effect as high pressure difference. In addition, it is shown that the steam-chamber-expansion angle is a function of pressure difference. Using this finding, a new mathematical model is established considering the modification of the expansion angle, which (Butler 1991) treated as a constant. With the proposed model, production performance such as cumulative oil production and oil-production rate can be predicted. The steam-chamber shape is redefined at the rising stage, changing from a fanlike shape to a hexagonal shape, but not the single fanlike shape defined by (Butler 1991). This shape redefinition can clearly explain why the greatest oil-production rate does not occur when the steam chamber reaches the caprock.
Exploration in 2018 got off to a strong start when the Chevron-operated Ballymore well encountered 205 m of net oil pay in the US Gulf of Mexico. Drilled by Pacific Drilling’s Sharav deepwater drillship, the well reached a total depth of 8,898 m. Global discovered oil and gas resources and big project sanctions are expected to remain on the upswing through next year, according to separate industry outlooks from Rystad Energy and Wood Mackenzie. Internalizing lessons from a difficult last few years, operators are choosing investments more wisely and now better prepared to deal with volatile oil markets, the consultancies concluded. "Portfolios are set to weather low prices, and the recent slide in prices justifies the sector’s conservative mindset."
Na, Li (Faculty of Geographical Science, Beijing Normal University, 100875, Beijing, China) | Jinliang, Zhang (Faculty of Geographical Science, Beijing Normal University, 100875, Beijing, China) | Jinshui, Liu (Shanghai Branch, CNOOC Ltd., 200030, Shanghai, China) | Wenlong, Shen (Shanghai Branch, CNOOC Ltd., 200030, Shanghai, China) | Hao, Chen (Shanghai Branch, CNOOC Ltd., 200030, Shanghai, China) | Guangchen, Xu (Faculty of Geographical Science, Beijing Normal University, 100875, Beijing, China)
Summary The prediction of source rocks is very important to the basin at the initial stage of exploration, among which the description of the source rocks' spatial distribution and the evaluation of the source rocks' thickness are the most significant. For most of the oil and gas fields on the land, the prediction and evaluation of source rocks rely on geochemistry analysis. But well data is inadequate on the offshore exploration area. Therefore, seismic data and geophysical methods can be applied to improve the prediction accuracy of source rocks. Data and Method In this research, the main data relate to core, logging, seismic from Lishui Sag, China (Figure 1).