Моделирование гидроразрыва пласта

Гидравлический разрыв пласта

Гидроразры́в пласта́ (ГРП) — один из методов интенсификации работы нефтяных и газовых скважин и увеличения приёмистости нагнетательных скважин. Метод заключается в создании высокопроводимой трещины в целевом пласте для обеспечения притока добываемого флюида (газ, вода, конденсат, нефть либо их смесь) к забою скважины. Технология осуществления ГРП включает в себя закачку в скважину с помощью мощных насосных станций жидкости разрыва (гель, в некоторых случаях вода, либо кислота при кислотных ГРП) при давлениях выше давления разрыва нефтеносного пласта. Для поддержания трещины в открытом состоянии в терригенных коллекторах используется расклинивающий агент — проппант, в карбонатных — кислота, которая разъедает стенки созданной трещины.

A ‘‘typical’’ hydraulic fracturing treatment starts with the creation of an initial path for the fracture. This is usually achieved by a technique called ‘‘perforation’’ in which specially designed shaped-charges are blasted on the wellbore walls with given orientations, perforating the casing and creating finger-like holes or weak points in the hydrocarbon-laden formation. A viscous fluid is pumped inside the wellbore, inducing a steep rise in the pressure which eventually leads to the initiation of a fracture at the perforated interval. A ‘‘pad’’ of clean fluid is usually pumped first, to provide sufficient fracture width for the proppant that follows. Proppant is injected at a later stage as a suspension or slurry. The treatment usually takes place on a time-scale of tens of minutes to a few hours, depending upon the designed fracture size and volume of proppant to be placed. At the end of the treatment, when pumping stops, leak-off of the residual fracturing fluid into the porous reservoir allows the fracture surfaces to close onto the proppant pack under the action of the far-field compressive stresses.

Физические процессы, сопровождающие гидроразрыв

Основные процессы:

• the mechanical deformation induced by the fluid pressure on the fracture surfaces
• the flow of fluid within the fracture
• the fracture propagation.

Additional complications

• the presence of layers of different types of rock (even if these layers are assumed to be parallel);
• changes in magnitude and/or orientation of the in situ confining stresses;
• the presence of a nearby free surface (of importance in the modeling of magma-driven dykes and in caving applications in mining);
• the leak-off of fracturing fluid from the fracture to the surrounding rock (or the invasion of reservoir fluid from the rock into the fracture), which is a history-dependent process;
• the effects of shear and temperature on the fracturing fluid rheology;
• the transport of suspended proppant particles within the fracture (of primary importance for oil and gas reservoir stimulations);
• modeling of fracture recession and closure (due to termination of pumping, forced flowback, or rapid geometric changes in one region as fractures herniate into other lower stress zones).