Sand control and sand management require a rigorous assessment of several contributing factors including the sand facies variation, fluid composition, near-wellbore velocities, interaction of the sand control with other completion tools and operational practices. A multivariate approach or risk analysis is required to consider the relative role of each parameter in the overall design for reliable and robust sand control. This paper introduces a qualitative risk factor model for this purpose. In this research, a series of Sand Retention Tests (SRT) was conducted, and results were used to formulate a set of design criteria for slotted liners. The proposed criteria specify both the slot width and density for different operational conditions and different classes of Particle Size Distribution (PSD) for the McMurray oil sands. The goal is to provide a qualitative rationale for choosing the best liner design that keeps the produced sand and skin within an acceptable level. The test is performed at several flow rates to account for different operational conditions for Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS) wells. A Traffic Light System (TLS) is adopted for presenting the design criteria in which the red and green colors are used to indicate, respectively, unacceptable and acceptable design concerning sanding and plugging. Yellow color in the TLS is also used to indicate marginal design. Testing results indicate the liner performance is affected by the near-wellbore flow velocities, geochemical composition of the produced water, PSD of the formation sand and fines content, and composition of formation clays. For low near-wellbore velocities and typical produced water composition, conservatively designed narrow slots show a similar performance compared to somewhat wider slots. However, high fluid flow velocities or unfavorable water composition results in excessive plugging of the pore space near the screen leading to significant pressure drops for narrow slots. The new design criteria suggest at low flow rates, slot widths up to three and half times of the mean grain size will result in minimal sand production. At elevated flow rates, however, this range shrinks to somewhere between one and a half to three times the mean grain size. This paper presents novel design criteria for slotted liners using the results of multi-slot coupons in SRT testing, which is deemed to be more realistic compared to the single-slot coupon experiments in the previous tests. The new design criteria consider not only certain points on the PSD curve (e.g., D50 or D70) but also the shape of the PSD curve, water cut, and gas oil ratio and other parameters.
Canada has enormous oil reserves which ranks third worldwide with proven oil reserves of 171 billion barrels. Alberta alone contributes with 165.4 billion barrels found in oil sands. However, the oil in oil sands is extremely viscous, and only 10% is recoverable through open-pit mining. In-situ thermal recovery methods such as Steam-Assisted Gravity Drainage (SAGD) have been developed and adopted as an efficient means to unlock the oil sands reserves. Different reservoir geological settings and long horizontal wells impose limitations and operational challenges on the implementation of SAGD technology. Wellbore trajectory excursions or undulations- unintentionally generated trajectory deviations due to suboptimal drilling operations- are some of the complications that lead to non-uniform steam chamber conformance, high cumulative Steam-Oil Ratio (cSOR) and low bitumen recovery. Conventional dual-string completion scheme (a short tubing landed at the heel, and a long tubing landed at the toe) has been widely adopted in most of the SAGD operations. Such configurations allow steam injection at two points: the toe and the heel sections of the horizontal well. However, these completions have demonstrated poor efficiency when reservoir/well complications exist. Tubing-deployed Flow Control Devices (FCD's) have been introduced to offer high flexibility in delivering specific amounts of steam to designated areas (such as low permeability zones) and ensure uniform development of steam chamber in the reservoir. The work in this thesis presents the results of a numerical effort for optimizing the design of Outflow Control Devices (OCD's) in SAGD wells for different scenarios of well pair trajectory excursions. A coupled wellbore-reservoir SAGD simulation model was constructed to optimize the placement and number of ports in every single OCD. Three different cases were generated from the constructed basic SAGD model with each case having a specific well pair trajectory which causes variable lateral distances between the well pair. Results of the optimized OCD's cases demonstrate a higher SAGD efficiency compared to their corresponding conventional dual-string cases. Those enhancements resulted in a higher steam chamber conformance, a higher cumulative oil production, and an improved Net Present Value (NPV).
The classical SAGD involves drilling wells in parallel horizontal pairs. Steam is injected into the upper well (injector) to heat the reservoir and mobilize bitumen so that it drains to the lower well (producer) and can be lifted to the surface. In this process, steam distribution in the injector and a sustainable liquid level above the producer are key to achieve steam chamber conformance. The completion designs of these wells are critical in order to achieve optimal bitumen recovery and steam chamber development. Two common tools in SAGD wellbore completions are Steam Splitters and Inflow Control Devices. The Steam splitters are used to customize steam distribution in the injector. The Inflow Control Devices are used in the producer to develop a uniform inflow along the horizontal wellbore. This paper presents a method for determining the size and position of Steam Splitters and Inflow Control Devices. This method can be used for both simple and complex reservoirs containing heterogeneous geology and hydraulic barriers and baffles.
The classical SAGD (Steam Assisted Gravity Drainage) involves drilling wells in parallel horizontal pairs. Steam is injected into the upper well (injector) to heat the reservoir and mobilize bitumen/heavy oil so that it drains to the lower well (producer) and can be lifted to the surface. In this process, steam distribution in the injector and a sustainable liquid level above the producer are key to achieve steam chamber conformance. The completion designs of these wells are critical in order to achieve optimal bitumen/heavy oil recovery and steam chamber development1. Orifice based Flow Control Devices (FCDs) are being used in the SAGD wells. The FCDs in the injector (Steam Splitters) are used to customize steam distribution along the well. The FCDs in the producer (Inflow Control Devices) are used to develop a uniform inflow along the horizontal wellbore. In this paper, a method will be presented for determining the size and position of Steam Splitters and Inflow Control Devices. This method can be used for both simple and complex reservoirs containing geological heterogeneity, hydraulic barriers and baffles. The validation of the design by field data in a Case Study will also be presented. It is shown that using FCDs in the wellbores helps to improve conformance and performance of SAGD well pairs significantly.
In the Steam Assisted Gravity Drainage (SAGD) process, the pre-heat is a very important step in the successful development of the steam chamber. The pre-heat period lasts months and is deemed complete when the temperature between the injector and producer is high enough to establish hydraulic communication. A uniform pre-heat along the wellbore is crucial to achieve steam chamber conformance throughout the life of the well pair. The efficiency of the pre-heat can be affected by several factors, with completion type being one of the most important among them. The objective of this study is to evaluate the impact of this factor on thermal efficiency during the pre-heat phase of the SAGD process. In this study, the completion practices in five major SAGD projects in Alberta, Canada (Suncor's Firebag and Mckay River, Cenovus' Christina Lake and Foster Creek, and ConocoPhillip's Surmont) were evaluated. The critical factor used to determine the efficiency of any completion type in the pre-heat process is the heat loss and heat exchange along the producer and injector wellbores and the completion components. This variation in thermal efficiency results from factors such as concentric versus eccentric dual tubing completion, and tubular size, length and configuration. The results of the study provide a comparison of different completion practices in the five major SAGD operations in Canada. The simulation modeling of the process, along with field experience and observations, helped to understand the impact of counter-current heat exchange and heat loss in concentric versus eccentric completions. Also, the results were used to quantitatively evaluate the impact that vacuum insulated tubing has on delivering energy to the reservoir and its associated thermal efficiency during the pre-heat process. This paper is aimed at providing a better understanding of the impact of different completion methods on thermal efficiency during the pre-heat period in the SAGD process. The study also incorporated actual field performance of the 5 major SAGD projects available in the public domain and AER reports.
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