Deep Water Completions in Campos Basin: Problems and Solutions
Authors: Plavinik B. , Juiniti R.B. , Paula M.T.R. , Dias R. 
Published: December 2007

The first question that arises when deep water completion (DWC) is discussed is the definition of deep water. This concept varies from company to company but Petrobras is considering deep water from 600m to 1200m water depth. From that depth until 3.000 m is ultradeep waters. DWC comprises many special equipment, mostly hydraulic operated. Most of the equipment under consideration in this paper may be similar to shallow water completion with Wet Christmas Tree (WCT) already installed but expertise, field experience and wide vision is crucial because the problems are fully different. This technical paper deals exactly with this subject. It intends to show few of the failures that Petrobras had in the last years with deep completion using wet christmas tree system. But more important than showing the failures or problems, the point is to analyze the solution that was given to all the problems. Knowledge, creativity, teamwork and patient were the basis for deriving this technology leader in the world.

Introduction

Deep offshore completion is still a rather new technology in our petroleum engineering world and many critical points still are under research(1). We could say that only in the last 3 years the 1.000m water depth was overcome mainly in countries as Brazil and the USA. In Brazil, the discovery of Marlim, Albacora, Bijupira, Salema, Caratinga and recently Roncador fields in Campos Basin made possible for the Brazilian government petroleum company Petrobras to invest in deep water production technology(2). This paper will discuss only part of the production technology which is the completion engineering related solely to wellhead equipment. Wellhead equipment we mean all production equipment that are installed from the wellhead connector to the well christmas tree. This includes multifarious equipments as (1) Housing for the permanent drilling base; (2) Production Adapter Base and running tool; (3) Production Tubing Hanger and running tool; (4) Wet Christmas Tree; (5) WCT Tree Cap and running tool; (6) accessories as Completion Riser, Terminal Head and Corrosion Cap (Fig. 1). In deep water drilling and completion, most of the incidents which resulted in rig loss time in the last 7 years were collected in a special report called ROA or Report for Abnormal Operations. More than a 1.000 ROAs form a special database which comprises field experience of Petrobras in treating different problems in drilling and completion in deep water and, more important, the analysis, solution and recommendation for each case. In this technical paper few cases where selected for presentation trying to cover most of the equipment /technique already cited.

Main Production Wellhead Equipments

In this paragraph the main production wellhead equipment and components will be briefly described. The objective is to indicate how the equipments look like, how they work, common sizes and main parts (3).

Drilling Housing.

The drilling housing is part of the permanent drilling guide base and is connected to the top of the 20 in. casing (Fig. 2). In deep waters, the standard nominal external diameter is 16 3/4 in. After cementing the 20 in. casing, the housing stays about 2 m above the mudline and has the following purpose:to hold up the 20 in. casing;to be a seat for the next casing hangers;to provide connection and support for the Blow Out Preventer (BOP).

This housing has a H-4 profile which will allow the BOP H-4 connector to hold and resist hydraulic pressure, weight and mechanical stresses (Fig. 3).

Drilling Housing.

The drilling housing is part of the permanent drilling guide base and is connected to the top of the 20 in. casing (Fig. 2). In deep waters, the standard nominal external diameter is 16 3/4 in. After cementing the 20 in. casing, the housing stays about 2 m above the mudline and has the following purpose:to hold up the 20 in. casing;to be a seat for the next casing hangers;to provide connection and support for the Blow Out Preventer (BOP).

This housing has a H-4 profile which will allow the BOP H-4 connector to hold and resist hydraulic pressure, weight and mechanical stresses (Fig. 3).