Abstract

A new enabling technology of delivering long perforation gun strings and logging equipment into Extended Reach (ER) Wells using coiled tubing assisted by an innovative all hydraulic tractor is presented. Recent operational experience at Chayvo Field in Sakhalin Island Russia on the first ER well illustrates the new capabilities of this approach that delivered coiled tubing strings into a 9,375 meter well, performing multiple perforations and logging operations. Pre-operations equipment qualification testing and downhole modeling methodology for the project are discussed.Sakhalin Island surface equipment and bottom hole assemblies are described along with operational experience and lessons learned that successfully delivered heavy payloads into distant reservoirs beyond coiled tubing lockup.

Introduction

To meet the growing requirements for oil production and address increasing costs of oil and gas developments, highly deviated extended-reach (ER), horizontal wells are frequently required.Completions for these wells have resulted in new logging and perforation challenges.

The use of wireline for logging or perforation is not suitable for horizontal wells because it relies on gravity to convey its payload to the targets.Recently, wireline has been assisted with electric tractors that can provide some pulling force at the Bottom Hole Assembly (BHA); however, these types of assemblies have increasing difficulty with increasing depth because of power losses and heat problems

Effectively beginning around 1985 conveyance of perforation and logging equipment on coiled tubing (CT) was pioneered1.Since then, CT has been used to perform thousands of perforation and logging jobs through out the world.A major advantage of CT is to reduce the number of operational trips by carrying heavy assemblies, which is beyond the capacity of wireline.

With ExxonMobil's venture into the Chayvo Field in Sakhalin Island Russia (see Figs. A-1 and A-2), plans began for developing the offshore reservoir from a land based drilling rig using ER wells.As described in Extended Reach Drilling Technology Enables Economical Development of Remote Offshore Field in Russia2 by McDermott et al., the expense with operating the remote location drilling rig necessitated consideration of completing these wells with CT.However, the extreme lengths of these wells required the use of specialty built CT equipment and a CT hydraulic tractor, herein described.

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