Abstract

In the Bay of Campeche, Mexico Marine operators have recently commenced the development of their high pressure, high temperature (HPHT) oil and gas fields in order to meet the high demand. These new developments present tough conditions for all aspects of well drilling and completion activities. They are particularly challenging for performing well intervention, which have driven operators, manufacturing and service companies to develop innovative strategies for servicing these fields.

For HPHT well developments, electric line conveyed guns is the most common technique employed to perforate wells in the area, whether dynamic or static conditions. Nevertheless, coiled tubing (CT) deployed perforating has been recently employed as a reliable option in the following cases:

  • Electric line is not a technically suitable option due to the limited magnitude of under-balance at which it can safely operate.

  • Drag and buoyancy forces encountered in the wellbore are close to the operational limits of the cable.

  • Wellbore tortuosity, tubular restrictions and well configuration render electric line unable to access perforation target depth.

Initially, this paper discusses the workflow for performing technical analysis to develop safe and economical CT conveyed perforating operations for HPHT wells in offshore Mexico, which considers CT string design, surface equipment, well control equipment and associated downhole tools. It then presents case histories and lessons learned. And finally, provides conclusions and recommendations from the experiences gained for performing HPHT CT deployed perforating activities in Mexico Marine.

Introduction

HPHT define well conditions above what is considered normal levels of pressure and temperature. For Mexico Marine operators any well intervention with wellhead pressure (WHP) above 3,500 psi and bottomhole temperature over 150 oC (BHT) is considered HPHT.

The Bay of Campeche is located at the southeast of Mexico in the continental platform of the Gulf of Mexico in front of Tabasco, Campeche and Yucatan coasts (Fig. 1). In 2004 Mexico Marine operators started to develop in the Bay of Campeche a significant number of fields that meet HPHT definition.

In Mexico Marine HPHT fields, electric line conveyed gun is the most common technique employed to perforate wells. However, CT conveyed perforating has been recently proved as an excellent option in cases where electric line restricts under-balance magnitude for safe operation, drag and buoyancy forces encountered in the wellbore are close to the operational limits of the cable, and tubular restrictions and well configurations may be a concern to access perforation target depth.

Mexico Marine HPHT Environment

HPHT developments (Fig. 2) in the Bay of Campeche target Cretaceous (K) and Upper Jurassic Kimmeridgian (UJK) formations. Cretaceous is a naturally fractured carbonate formation ranging depths from 4,500 to 5,500 m with Porosity ranges from 3.0 to 5.0% and Permeability of 18 md. Upper Jurassic Kimmeridgian is a dolomitized carbonate formation in Oolitic banks from 5,000 to 6,000 m, where Porosity ranges 5.0 to 8.0% with Permeability from 20 to 40 md.

The new fields under development are highly pressurized with bottomhole pressure (BHP) from 10,000 to 12,000 psi and BHT up to 190 oC. In surface, shut-in pressures from 6,000 to 8,500 psi have been recorded, and hydrocarbon production is composed by gas and oil from 27.0 to 48.0 oAPI.

Drilling operations are performed by jackup rigs from eight-leg fixed platforms in water depths up to 60 m. Well deviation ranges 0 to 60 o, and jackup rigs are also the most common structures available for well completion and workover operations. These rigs have a limited crane capacity of 30 ton to lift and position CT string onboard.

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