Surface BOP: Testing and Completing Deepwater Wells Drilled With a Surface-BOP Rig

Abstract

Summary Many deepwater-development projects in operators' portfolios require lower costs to meet internal economic thresholds. Because of this, Shell has looked at extending surface-blowout-preventer (BOP) activities to include well testing and completion techniques for deepwater wells in conjunction with surface-BOP drilling. The cost advantages of surface-BOP-drilled wells have been demonstrated(notably in the Far East), but the recent surface-BOP-drilled well in Brazil is a milestone in terms of extending the applicability to deeper water and harsh erenvironments. The enabling technology has been the subsea isolation device(SID).Testing and completion techniques have been developed to be compatible with surface-BOP wells drilled with an SID. This paper focuses on the following aspects:•Well testing using surface-BOPs from a moored rig and•Well completions using surface-BOPs from a moored rig. Shell has developed a testing configuration to carry out a DST, essentially using standard equipment. The well-testing equipment configuration is currently ready for use and has been run in a subsea-BOP well. In completion operations, the availability of a high-pressure (HP) riser does not add significant complexity and even actually simplifies some of the completion activities. Conceptual studies and early hazard/risk assessments have shown there are no obvious "showstoppers," and the duration of a surface-BOP-rig completion is expected to be very similar to a subsea-BOP-rig completion. This paper describes the results of the conceptual studies, early hazardassessment exercises used to define the basic design parameters, and more detailed hazop studies. Introduction As deepwater exploration and development move into even deeper water and more arduous environments, operators are looking at ways to reduce well costs to make prospects and developments economically more attractive. One of the key avenues seen to do this is to accomplish drilling, testing, and completing wells by use of smaller deepwater rigs, consequently resulting in a reduction in rig rates. Surface-BOP technology facilitates the deployment of smaller rigs in deeper water, thus lowering day rates, well costs, and field-development costs. To date, most ultradeepwater wells (in which water depth is greater than5,000 ft) have been executed using the latest generation of new or converted drilling vessels (these will be referred to as "Generation V" rigs).Over150 subsea wells in varying water depths have now been executed with floating rigs with surface-BOPs in locations around the world. In 1967, a semisubmersible rig (Sedco-135) was used to drill a subsea well by use of surface-BOPs offshore Nigeria in EA-3.Since then, a number of operators have pioneered the use of surface-BOPs with moored rigs in the benign environmental conditions of the Far East. Shell has recently used surface-BOPs on a Generation V dynamically positioned (DP) rig to extend the7,500-ft-water-depth capability of the rig—drilling a deepwater exploration well in 9,474 ft of water offshore Brazil.1 The trend is to take this technique and apply it in a number of deepwater-operating areas with older Generation III and IV rigs that were not specifically built for deepwater operation. This paper outlines the well-testing and well-completion approaches that are planned to meet these challenges. The overall surface-BOP system will be described followed by the description of well-testing and well-completion methodologies. It should be noted that these methodologies are continuously worked on and refined; once actual experience is gained, they will, of course, change and be further optimized.

Subsea blowout preventer (BOP): Design, reliability, testing, deployment, and operation and maintenance challenges

“…In deep and UD water depths, the accumulator bottles could become prohibitory due to increased expense and floater capability to handle such large LMRPs. At these depths however, charging and replenishing accumulator canisters can only be done by remotely operated vehicles (ROV) intervention, an area of continual questionable reliability [123]. As the Emergency Disconnect System (EDS), Deadman switch and blind shear rams depend solely on the proper functioning of hydraulics, independence from main controls in the event of blackouts and loss of power are vital.…”

“…In recent years, the third and fourth generations of BOP systems have become popular. The new systems employ casing risers in place of flexible tube risers and a Subsea Isolation Device (SID), placed on the seabed [123]. A Subsea Deployment System (SDS) has also recently emerged, making use of a fully floodable solid buoyancy hull with chains attached to float equipment being deployed in water [125].…”

Workflow to Evaluate Maximum Allowable Treating Pressures, Tubing Movement, and Tubular Limits for Deepwater Subsea and Dry-Tree Fracpacks

“…When completing wells with subsea wellheads (production wellhead location on seafloor), generally a subsea BOP stack is used. Mason et al (2005) generated a standard surface vs. subsea stack configuration (Fig. 2).…”