Technical Paper: A novel approach to fracturing height control enlarges the candidate pool in the Ryabchyk formation of west Siberia's mature oil fields

Society: SPE
Paper Number: 107604
Presentation Date: 2007
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The productive pay of the low permeability Ryabchyk formation in the mature fields of Western Siberia is separated from underlying water zones by a weak stress barrier.

Operating and service companies alike applied various techniques to prevent the breakthrough of hydraulic fractures into the underlying water zone, but so far without clear success.

The paper describes a technique of physical barrier placement and tailoring fracturing fluid systems to control fracture net pressure development, that combined is used to mitigate fracture height growth. The method consists of pumping a predetermined mixture of specialty solid materials. The case study clearly demonstrates the challenges encountered in the attempt to increase the fracture half-length in order to improve the fracture treatment and the increasingly difficult task of simultaneously controlling fracture height growth. In addition to the risk of the post-frac increase in water-cut, the uncontrolled fracture height growth into the water zone is also considered to be a major cause of premature screen-outs. This is particularly true in cases when largemesh-size intermediate strength proppants are used.

The systematic application of the technique resulted in the increase of the average measured net pressure from 14 to 27 bars at the end of the main treatment, indicating fracture containment within the pay zone. The contained fractures manifest a 4 times liquid and 3.2 times higher average oil production compared to the production before the fracturing treatment. The new fracturing method, when compared to the conventional fractures placed in the past, resulted in the decrease the post-frac water cut from 75 to 46% while at almost no impact in average oil rate.

The paper provides a summary of the solution, which allowed the operating company to proceed with successful fracturing activity in the Ryabchyk formation.