Atlantic Richfield Company

C Mark Pearson

Ahmed S Abou-Sayed

Fevzi Zeren

Hydraulic fracturing of earth formations from wells for producing gas or hydrocarbon liquids is carried out by extending the fracture to a predetermined length with clean or low proppant concentration fluids, then decreasing the rate of injection with low proppant concentration fluids to equal the fluid leakoff rate until the fracture tip is blocked or screened out. Alternatively, the proppant concentration could be progressively increased until tip screenout occurs. Injection rates are then increased, particularly in high permeability formations, to increase the fracture width.

Rate control method for hydraulic fracturing

Certain wellbore fluid stimulation treatments may be monitored by a system including instrumented manifolds which may be connected between a base fluid source and a blending unit and between the blending unit and fluid injection pumps, respectively for measuring flow rates of the base fluid, the fluid additives and the fluid composition formed by the base fluid and the fluid additives. Instruments are also provided for measuring fluid temperature, pH, viscosity and flow behavior indexes (n', K') and fluid density. Quality control and determination of pressure losses in the wellbore together with modeling of stimulation treatments may be carried out by the continuous monitoring of parameters with the base fluid manifold and the mixed composition manifold.

System for monitoring fluids during well stimulation processes

Friction pressure losses are obtained for non-Newtonian or generalized Newtonian fluids being pumped through conduits at high flow rates, such as in hydraulic fracturing of subterranean formations, by measuring friction pressure losses in a pipe viscometer under laminar flow conditions. The pipe viscometer includes a pump which supplies fluid to a continuous loop having three pipe sections of different diameter for measuring pressure drop at different flow velocities. Sets of data points of generalized shear stress and shear rate are measured for determining the consistency index (K') and the Power Law or flow behavior index (n'). The generalized Reynolds number of the fluid being pumped is determined using the values of consistency index and flow behavior index and this Reynolds number is maintained in a second pipe viscometer section arranged in parallel with the laminar flow loop by pumping the same fluid wherein the second pipe viscometer section has the same roughness as the conduit through which friction pressure loss is to be determined. The Fanning friction factor (f) is determined for the pipe viscometer section from known values of friction pressure drop over a predetermined length of the pipe viscometer section at a known flow velocity, known fluid density and known hydraulic radius of the pipe viscometer section. The actual pressure drop over a predetermined length of conduit is determined using the calculated value of friction factor (f) and measured values of fluid density, flow velocity and conduit dimensions.

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Plano, TX, United States of America

C Mark Pearson