Downhole equipment, tools and assembly procedures for the drilling, tie-in and completion of vertical cased oil wells connected to liner-equipped multiple drainholes

Abstract

Single horizontal wells drilled through heterogeneous reservoirs are capable of greater oil productivity than vertical wells, often with lower produced GOR and WOR. Multiple drainholes tied-in to a vertical cased well are even more beneficial. Completion of such drainholes in many sandy reservoirs must use cemented liners. Well configurations comprising multiple drainholes liners, each of them tied-in to a vertical casing by pressure-tight connections require novel technologies making use of some novel downhole equipment, tools and procedures for drilling, tie-in and completion of such wells. These may be for newly-drilled wells or may be obtained by re-entry into an existing vertical cased well. Specific equipment, including novel casing joints, whipstocks, intermediate liners and tubing completion assembly components applicable to new wells are described herein. Equipment comprising novel casing inserts and patches applicable to re-entry wells, and the corresponding tubing completion assembly components for a variety of well exploitation modes are also described, together with the required tools and procedures. The liners of the drainholes are such that known well logging and cleaning tools may be used throughout the well's life. The various tubing completion assemblies can all be run-in and installed in a single trip. They allow either commingled flow from all drainholes or selective injection into some drainholes while others are under production. They are adapted to a variety of reservoir pressure conditions and of oil types, including heavy oil produced by sequential "huff and puff" steam injection.

Description

FIELD OF THE INVENTIONHorizontal wells have been used extensively in heterogeneous reservoirs to intersect fractures and / or to reduce the detrimental effects of gas coning and water coning. It has been shown that such wells are capable of higher oil production rates than vertical wells drilled in the same reservoir. In most cases, the higher productivity more than offsets the higher cost of drilling and completion of the horizontal well. Theory predicts that the use of multiple horizontal drainholes correspondingly multiplies the total well productivity. Indeed many vertical cased wells connected to twin or multiple horizontal drainholes of medium (500-200 ft) and short (150-40 ft) radius of curvature have been successfully used in compact oil reservoirs, such as the Austin Chalk, in which open hole completion of the drainholes is applicable.In many clastic reservoirs, however, the strength of unconsolidated sands or of friable sandstones may be insufficient to keep horizontal drain...

AI Technical Summary

Benefits of technology

The present invention addresses the problem of drilling, cementation and tie-in by pressure-tight connections to a casing of twin or multiple drainholes of medium to short radius of curvature (typ...

Problems solved by technology

The simplest, which allows only commingled flow from or into all drainholes simultaneously, does not even requires any additional equipment if vertical flow is through the casing, but it provides minimum operational flexibility and no safety controls.

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