Abstract

Hydraulic fracturing has been extremely successful in the western desert of Egypt, with approximately 85% of the production resulting from the use of this stimulation technique. However, in many cases the proximity of producing zones to underlying (or overlying) water zones can be a deterrent to fracturing. In the absence of geological barriers, the fracture height can grow uncontrolled during a fracturing treatment into the water-bearing interval and cause unwanted water production. Excessive water production can be detrimental to the economics of a well. By shortening the well's production life and increasing disposal and lifting costs, excessive water production can be extremely detrimental in marginal fields.

This paper presents case histories in which wells were hydraulically fractured using conventional techniques, resulting in higher than 60% water cut, even as much as 100% in one case. While using the conformance-while-fracturing (CWF) method, the water cut was as low as 4%, even when the adjacent water zones were within 20 ft of the perforations. This technique provides a tremendous boost to the economics and an effective solution to a field otherwise plagued with water overproduction. The CWF technique incorporates a relative permeability modifier (RPM) in the fracturing-fluids design. The RPM results in a reduction of effective permeability-to-water without significant changes to the relative permeability-to-oil. This paper describes the geological environment of the El Dour field and discusses properties of the RPM, the CWF job-design considerations, its field applications, and post-fracturing results in comparison to offset wells fractured conventionally. These techniques might be beneficial to other companies faced with similar water-production challenges.

Introduction

As the world's oil-energy demand increases, challenging reservoirs are now being explored. One of the biggest challenges is the water production that normally accompanies the hydrocarbon production. The water can trap the oil and leave huge hydrocarbon reserves unrecovered and also accelerate the fines-migration problem. During well completion, water can increase the chances of corrosion to the surface, downhole tubular, and the chances of scale formations, which can be very difficult to remove once formed (Curtice et al. 2008).

An example of a challenging reservoir is one that does not produce normally without hydraulic-fracturing treatments and has water zones very near to the hydrocarbon zone.

Once these reservoirs are completed using hydraulic fracturing, the water production increases. The problems caused by the water production can be difficult to solve. The case presented in this paper involves one of these reservoirs located in southern Cairo in the western desert, called El Diyur field.

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