A discussion of the problems associated with fracture height containment in several producing horizons in East Texas is presented along with a field-proven solution. Fracture height containment has plagued operators in East Texas for years. Fracturing of producing intervals, such as the Georgetown, Buda, producing intervals, such as the Georgetown, Buda, Woodbine, Travis Peak and Pettit Line, has in many cases resulted in unsatisfactory production. The poor production can in many cases be attributed to poor production can in many cases be attributed to fracturing out of zone. A technique has been developed to minimize fracture height growth. This patented technique incorporates non-reactive patented technique incorporates non-reactive diverting agents to bridge above and below the pay zone. This results in a planned screenout in the vertical directions thus forcing the fracturing fluid to propagate the fracture in the horizontal direction.
Several case histories are presented to show the effectiveness of the technique.
Failure to contain fracture height growth during hydraulic fracturing treatments often renders uneconomical results which drastically alter pay-out, overall hydrocarbon recovery and profitability. Problematic production of water from outside the zone Problematic production of water from outside the zone of interest can rarely be reversed. Here the operator incurs the additional expense of water disposal mad decreased hydrocarbon inflow at the wellbore. Likewise, vertical growth into a gas cap in most cases is undesirable from the standpoint of decreased primary recovery.
The predictability of fracture geometry is fast becoming an economic issue. Decreased frac height in a controlled example means increased fracture length as opposed to an uncontrolled situation. Regardless of the model employed, production is a function of fracture conductivity. Equation 1 shows that dimensionless frac conductivity (F) is sensitive to CD fracture length and fracture width.
k F = f w CD (1) k × f
If the proppant is not contained in the zone of interest, excessive frac height results in narrowing the propped width. The treatment will not be optimum; it may not be economical.
Several methods of restricting fracture height during hydraulic treatments love been tried where lithologic barriers are known to be weak or nonexistent.
Cannon techniques previously employed in East Texas include:
fracturing with compressible (N2 foam) fluids;
reducing treatment injection rates to limit pressure applied to barriers;
restricting fluid viscosity and density to minimize pressure applied to barriers;
combinations of the above.
Obviously, foam fracturing is not always feasible, nor are the other options listed above. Limiting the injection rate risks screenout due to high leak-off in permeable zones, naturally fractured zones, and in zones with no barriers. restricting fluid viscosity on treatments where extended pump times are required results in decreased width, excessive frac fluid, and often screenout in high temperature wells. Decreased prop concentrations yield less fracture conductivity prop concentrations yield less fracture conductivity and thus, less productivity.