Hydraulic fracturing methods using cross-linking composition comprising delay agent

Abstract

A method for hydraulically fracturing a subterranean formation comprises introducing into the formation a cross-linking composition which comprises (a) an aqueous liquid, (b) a pH buffer, (c) a cross-linkable organic polymer, (d) a cross-linking agent which comprises an organic titanate, an organic zirconate, or combinations thereof, and (e) a delay agent which is a hydroxyalkylaminocarboxylic acid. The method can be used over a wide range of pH conditions.

Description

FIELD OF THE INVENTION [0001] The invention relates to the field of oil well fracturing using a cross-linking composition. The cross-linking composition comprises a cross-linking agent which is a zirconium or titanium complex or mixtures thereof, a cross-linkable organic polymer and a delay agent. BACKGROUND OF THE INVENTION [0002] The production of oil and natural gas from an underground well (subterranean formation) can be stimulated by a technique called hydraulic fracturing, in which a viscous fluid composition (fracturing fluid) containing a suspended proppant (e.g., sand, bauxite) is introduced into an oil or gas well via a conduit, such as tubing or casing, at a flow rate and a pressure which create, reopen and / or extend a fracture into the oil- or gas-containing formation. The proppant is carried into the fracture by the fluid composition and prevents closure of the formation after pressure is released. Leak-off of the fluid composition into the formation is limited by the f...

AI Technical Summary

Benefits of technology

[0010] The present invention provides methods for effective delaying the action of titanium and zirconium cross-linking agents in oil field applications. Surprisingly, a range of temperature, pH and other conditions can be tolerated and delay times controlled to provide flexibility by adjusting relative amounts of components, including cross-linking agent and delay agents.

Problems solved by technology

Normally, less than one third of available oil is extracted from a well after it has been fractured before production rates decrease to a point at which recovery becomes uneconomical.

Ideally, such techniques (commonly called flooding techniques) provide a bank of oil of substantial depth being driven into a producing well; however, in practice this is frequently not the case.

Rather than developing new cross-linking agents for these new conditions, the oil well service companies may add delay agents that effectively delay the cross-linking of a particular metal cross-linking agent under these conditions.

There are only a limited number of disclosed delay agents suitable for titanium and zirconium cross-linking agents.

Thus, use of delay agents with titanium and zirconium cross-linking agents has limited flexibility for use by the oil well service companies to stimulate or enhance recovery of oil or gas from a well or other subterranean formation.