Non-uniform steam chamber caused by reservoir heterogeneity, shale interlayer, local mobile water, undulating well trajectories and improper operation, etc., severely restricts oil sands SAGD performance. Inflow control devices (ICD) achieved great success in controlling conventional water or gas coning. Inspired by this, liner and then retrofitting tubing deployed ICD have been tested since 2009 and soared in recent years. Therefore, this paper made a systematic review of ICD design, operation principle and application evaluation. Different types of ICD applications in dozens of Canadian oil sands projects were comparatively investigated including operating principle, adaptability analysis, liner-deployed or tubing-deployed ICD, early-to-medium SAGD performance. Then a numerical simulation method incorporated the relationship of pressure drop versus mass rate at different conditions and pressure degradation due to erosion impacts is presented. The feasibility analysis of ICD deployed on injector or producer was further evaluated by numerical simulations. Besides, a set of ICD optimization design method is provided including the principles of well selection, reasonable ICD number along horizontal well section, and optimum operating conditions, etc. Revolutionary ICD technology has become an effective way of greatly improving SAGD performance in recent years. According to the statistical data, most ICD are deployed on producers rather than injectors, which is also explained by numerical simulations of technical feasibility evaluation. In order to deal with uneven steam chamber growth, the number of tubing deployed ICD dramatically increases in recent years. The proportion of liner and tubing deployed ICD is 58% and 42%, respectively. However, there are big differences in SAGD performance of different ICD wells. Some ICD wells is worse in SAGD performance and even damaged by sand production. Based on absorbing the knowledge of field application, the behavior of different types of ICD was compared to guide the selection. Then the workflow of ICD optimization design method was provided by calculating conformance and allocated liquid volume according to the relationship of pressure drop versus mass rate. The operation principle is suggested to facilitate lower subcool but zero subcool not allowed in long term due to sand production risk. On the basis of reasonable well selection, it can easily improve conformance by above 15% and oil production by over 50%. Inspired by this, ICD also applied to several multilateral SAGD well pairs to balance steam or liquid distribution along horizontal wellbore. This paper first systematically provides various types of ICD behavior, screening criteria, design practices, operation principle and application evaluation in SAGD process. These findings are very useful for ICD design and enhancing both oil recovery and thermal efficiency in heavy oil or bitumen production.

SAGD process has been widely applied in super-heavy oil and oil sands projects. Slow vertical steam chamber growth and non-uniform conformance tends to generate lower oil rate and higher steam to oil ratio in SAGD projects, which were mainly influenced by thin pay, shale interlayers and bottom transition zone. Therefore, this paper presents screening and evaluation results of many emerging technologies to develop super-heavy oil or oil sands projects. 15 kinds of new technologies were investigated by AER reports and numerous papers. 6 of them were evaluated by numerical simulation, including multilateral injector or producer, vertical slimholes assisted SAGD process, steam drive assisted gravity drainage, offset SAGD well pair, and bottom-up gravity-assisted pressure drive, etc. Besides, the experience of field practices related to many little-known emerging technologies was extensively and deeply analyzed including single vertical well SAGD process, fishbone wedge producer, liner or tubing deployed ICD/FCD, various dilation practices in preheating or SAGD phase, movable steam splitter, re-drill injector or producer with optimized location, steam drive assisted gravity drainage, etc. Moreover, the mechanisms, detailed pilots and challenges were further summarized. For thin pay, single vertical well SAGD process aims to realize vertical multi-stage fracturing based on expansion pipe, accelerate steam chamber growth from top to the bottom, maximize the effect of gravity drainage to achieve earlier peak oil rate. For the reservoir impacted by shale laminae, steam drive assisted gravity drainage under different well spacing can be trialed. Steam circulation or stimulation, hydraulic fracturing and multilateral producer may be applied from 5m, 10m to 20-30m horizontal spacing while keep vertical spacing at 3-5m. Besides, enhancing vertical permeability, drilling vertical channels or enforcing horizontal driving force are possible solutions to overcome shale interlayers and bottom water. Dilation process assisted by waste water, polymer, chemical or low cost catalyzer in more than one hundred well pairs can reduce steam consumption in start-up process and achieve better early SAGD performance. Bottom-up gravity-assisted pressure drive process overwhelms SAGD process in terms of accelerated oil production and lower SOR in relatively low quality oil sands projects such as thin pay, shale interlayers, bottom transition zone, etc. Especially, the practices of wedge wells, multilateral injector or producer, steam drive assisted gravity drainage based on multilateral producer, and re-drill injector or producer successfully tapped the remaining oil, enhanced the peak oil rate or reduced SOR significantly. This paper presents much novel information about research advancement and field practices of many new technologies. These technologies can be effectively applied to relatively low quality heavy oil projects such as thin pay, shale interlayers, bottom transition zone, etc.

Steam assisted gravity drainage (SAGD) using parallel dual-horizontal wells made great success in developing heavy oil or oil sands projects. However, the performance may be greatly impaired when shale laminae with high frequency exist. In order to enhance oil production and decrease steam to oil ratio (SOR), this paper conducts feasibility study of offset well pair using steam drive and gravity drainage to develop oil sands project by overcoming shale laminae. Physical simulations of offset well pairs under three horizontal distance were first carried out to analyze the mechanism. On the basis, homogeneous model and heterogeneous model incorporating staggered shale laminae were constructed, respectively. Then numerical simulations of conventional SAGD well pair and offset well pair using steam drive and gravity drainage were conducted to evaluate the influence of pay thickness and possibility of mitigating adverse impact of shale laminae. Moreover, several configurations of offset well pairs and their application results were proposed. The results of physical simulations indicate that there is larger lateral steam chamber development compared with conventional well pair. While for numerical simulations, for homogeneous case, compared with conventional well pair, offset well pair achieves similar performance but delaying oil production for 0.5 year, and the performance cannot be improved significantly even if aggressive pressure difference or subcool control is enforced. But for heterogeneous model with existing inter-well shale laminae, offset well pair can significantly improve early to mid-term performance and accelerate early steam chamber growth by enforcing pressure difference. But once steam chamber has grown to a certain height, there is no big difference between offset and conventional well pairs. Furthermore, three configurations of offset well pairs are evaluated including the injector drilled 3 m high and 4 m laterally from the producer, offset horizontal injector and multilateral producer, and multi-stage hydraulic fracturing or dilation assisted enlarge well spacing of 10-30m. Encouragingly, offset horizontal injector and multilateral producer has made great success by a combination of steam drive and gravity drainage in Canadian Surmont oil sands project. The proposed technology was first studied by combined physical and numerical simulations, and it can be effectively applied to relatively low quality oil sands projects such as thin pay and challenging pay with staggered shale laminae. Several configurations of offset well pairs have been listed as pilot suggestions.

SAGD technology has been successfully and widely applied in the development of superheavy oil and oil sand projects. Before normal SAGD process, some preheating ways are often needed to realize interwell hydraulic connection, and this means that determining reasonable SAGD conversion timing from the preheating stage is an essential precondition for good performance. Previous numerical simulations or qualitative analysis of temperature fall-off data are often adopted in the industry, but they have deficiencies in terms of dependent on static geological model or insufficient data utilization. Therefore, on the basis of the temperature and pressure monitoring process comparison in China’s superheavy oil and Canada’s oil sand projects, this paper proposed a temperature fall-off interpretation model to obtain thermal diffusivity and preheating radius at different measurement points along the horizontal section by combining an unsteady thermal conduction model under constant heating power of wellbores in the radial coordinate system and approximately unsteady thermal conduction model with constant wellbore temperature and Fourier’s law of thermal conduction. Besides, the duration time, interpretation method, and application flow chart of temperature fall-off test were presented. Then, it was validated to successfully determine the timing of SAGD conversion from the preheating stage by an example combining with tracking numerical simulation, temperature inflection point analysis, and index analysis during the partial-SAGD and initial SAGD stages. The findings of this study can help determine the SAGD conversion timing from the preheating stage simpler and faster especially for the case of long horizontal well section deployed with more temperature measurement points.

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