There are several different types of reservoirs that have a high degree of natural fracturing. In these reservoirs, the fluid loss mechanisms are more complicated than those found in more coherent formations. The loss of fluid to intersecting fractures is especially important in the fracturing of coalbeds, Devonian type shales, limestones and naturally fractured sandstones. In many cases, the reservoir permeability is often such that the fluid loss to these fractures is the primary fluid-loss mechanism. Little is known "about how to handle this type of fluid loss in fracture simulation calculations, or the effects of this fluid-loss mechanism on pressure drop in the fracture. While the loss of fluid to intersecting fractures is not the only fluid-loss mechanism in naturally fractured sandstone reservoirs, it can dominate the fluid loss to the reservoir under some conditions. Examination of the problem from both a computer based modeling and laboratory standpoint is clearly warranted.Flow of fluid down a fracture in a sandstone reservoir is modified by the continual loss of fluid to the reservoir through the permeability of the rock. In a naturally fractured reservoir, fluid loss occurs mainly at points where the fracture intersects an existing fracture in the rock. ThisReferences and illustrations at end of paper.

Even temperature conformance along the length of the horizontal well is key to maximizing Steam Assisted Gravity Drainage (SAGD) production rates. When temperature logs are run in SAGD producers, temperature variations of greater than 50°C between the hottest and coldest spots are commonly observed. We theorize that this temperature distribution is related to an inflow distribution, and that production rates could be improved if this temperature variance was narrowed.It is difficult to influence conformance with traditional SAGD producer well design. Flow areas are large, and liquid velocities are low, resulting in small frictional pressure losses. It is not possible to impose a materially different drawdown on hot and cold spots along the horizontal with typical well completion methods.A field trial is ongoing at the Firebag project in which a production well is equipped with intelligent completion technology. The test well's horizontal liner section is split into four hydraulically isolated zones, with each zone having the ability to provide flow or isolation from the reservoir. The well completion is equipped with optical pressure and temperature (P/T) gauges and distributed temperature sensing (DTS) technology which monitors each segment's performance during operations. The capability to independently and immediately manipulate each segment's production inflow will provide the operator the ability to evaluate the influence of an intelligent completion design on a well's conformance and ultimate oil recovery.

Steam Assisted Gravity Drainage (SAGD) is an enhanced oil recovery process whereby a long horizontal steam injection well is located above a long horizontal production well. Injected steam forms a steam chamber above the SAGD well pair, heating the reservoir rock and reservoir fluids. Heated oil (or bitumen) plus condensed steam flows down the sides of the steam chamber towards the production well. The condensed steam and bitumen are then lifted to surface with a downhole pump or by gas lift. Over the past decade, SAGD has become an increasingly popular method for extracting bitumen from Canadian oilsand leases that are too deep for surface mining, largely due to the high recovery factor from SAGD.Nodal analysis for oil and gas wells enables the user to model well production or injection performance from the producing reservoir to the surface gathering system. Nodal analysis for well performance is based on the principle that reservoir inflow and wellbore outflow can be independently characterized as functions of flow rate. The single rate that balances the pressure losses in the inflow-outflow components with the pressure drop across the total system defines well flow. Nodal analysis is used to design new wells and optimize production or injection on existing wells. In addition, wellbore simulations are cheaper than instrumentation, meters or single well tests. Well evaluation software is the most popular package in Suncor's conventional production engineering toolkit because it is very accurate and easy to use.Due to a rapidly increasing number of SAGD well pairs, Suncor required a tool that could accurately model these thermal wells. Over the past few years we worked with our software provider to develop nodal analysis for SAGD production wells, and we can now model SAGD producers with electric submersible pumps (ESP) with a high degree of confidence. The new SAGD nodal models quite closely match production rates, plus surface and downhole pressure and temperature data. Reliable and rigorous SAGD nodal models will enable improved decisions with respect to SAGD field development and production optimization. Definitions, Specific to SAGD• Subcool: The difference between the saturation temperature of steam at a specific pressure and the temperature of the produced fluid. • Quality (X): The proportion or percentage of vapour in a mixture of liquid and vapour, on a mass basis.