Hydraulic fracturing slurries

The various fields of chemistry play an important role in the discovery and exploitation of oil and gas reserves. Improved drilling and well completion fluids, cement slurries, hydraulic fracturing and acidizing fluids to improve well productivity, various chemical additives to be used in these fluids, and chemicals for enhanced oil recovery are essential to the improvement of production economics and to an increase in recoverable hydrocarbon reserves. Chemistry will become increasingly important in future hydrocarbon production with the decreased likelihood of major onshore discoveries, increased discovery and production costs associated with deep offshore wells and Arctic frontier provinces, and the decline in drilling since early 1982. 

Suspensions or slurries used for well stimulation are prepared by adding a known quantity of proppant to the carrier fluid of choice to obtain a desired proppant concentration. The proppant concentration is usually referred to as the amount of solids added in a gallon of carrier fluid. A 20-40 U.S. mesh size is the most commonly used proppant for hydraulic fracturing. However, other particle sizes such as 8-12, 8-16, 10-20, 12-20, and 40-60 mesh are also used. 

Hydraulic properties, that is, friction-loss calculations of proppant-laden fluids or slurries, are very important not only in the design of any hydraulic fracturing treatment but also in real-time monitoring of fracturing treatments. Recent advances (27, 28) in real-time fracture analysis have necessitated an accurate knowledge of bottomhole treating pressure (BHTP). To estimate BHTP, an accurate prediction of friction pressures of fluids in the flow conduit is required. It is possible to obtain the BHTP from the surface pressure with the following equation ... 

To design a successful hydraulic fracturing treatment for horizontal wells, accurate information on the transport properties of slurry in horizontal pipe is required. One must know the critical deposition and resuspension velocities of various fluids in horizontal pipe flow. 

Hydraulic fracture stimulations are overseen continuously by operators and service companies to evaluate and document the events of the treatment process. Every aspect of the fracture stimulation process is carefully monitored, from the well head and downhole pressures to pumping rates and density of the fracturing fluid slurry. The monitors also track the volumes of each additive and the water used and ensure that equipment is functioning... 

High-pressure squeeze cementing operations are utilized where the hydraulic pressure is used to make new channels in the rock formations (by fracturing the rock) and force the cement slurry into these channels. 

Low-pressure squeeze cementing operations are utilized where the existing permeability structure is sufficient to allow the cement slurry to efficiently move in formation without making new fracture surfaces with the hydraulic pressure. 

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