Safely Improving Production Performance through Improved Sand Management

Abstract

Many operators implement a conservative approach to sand management implementing a "Zero Sand Production" or "Maximum Sand Free Rate" Criteria. This is due to the potentially severe consequences associated with sand production i.e. erosion, and the fact that existing standards and guidelines /1/ do not provide sufficient practical advice on how to manage erosion issues during operations. These criteria generally put restrictions on the production rate (and revenue) to reduce sand production and decrease the risk of erosion leading to a loss of containment. These restrictions are in many cases unnecessary.

This paper describes the development of an alternative approach which improves the production and safety performance of fields that are capacity restrained due to sand problems. The development of the approach started with a project for Conoco 1996 - 2000 /2/ and was further refined on a pilot project for Statoil in 2001 /3/, where it received the Statoil prize for the most successful R&D project in 2001.

From an erosion perspective the amount of sand produced is only one of many factors that must be managed; equally important factors are sand particle velocity, impact angle and material grading. By gaining a better understanding of the specific erosion characteristics of a field through: well sand risk ranking, identification of erosion critical components and detailed erosion assessment including 3D computer modeling; a more sophisticated erosion management strategy can be implemented identifying specific asset operational criteria, erosion monitoring and inspection requirements.

Implementation of this erosion management approach has provided operators with enhanced production, reduced inspection and maintenance costs without compromising safety and environmental targets and increasing/enhancing business performance.

Introduction

The mid / late 1990's saw a significant increase in unplanned hydrocarbon releases for Conoco in one of their UK North Sea operations. The releases occurred on manned installations and unmanned satellite installations with significant business and safety impact. The root cause of all incidents was an increase of solids production leading to accelerated erosion, see figure 1 for typical damage. The implemented solution of a revised Solids Management Strategy, the Maximum Allowable Solids Rate approach, has led to increased production, reductions in operating costs and enhanced safety performance.

Challenges

The key challenges in the implementation of the revised strategy can be broadly summarised as follows:

Resistance to Change

Operations personnel had over a long period of time assumed that adoption of a ‘solids free' production would minimise failures. In reality the measures adopted to achieve this aim led to an escalation in the number and severity of unplanned failures. A key challenge was education and confidence building amongst the workforce to achieve a ‘sea change' in the mind set and an improved understanding of the key issues.

Regulatory Pressure

The failures focussed regulatory attention due to their hazardous nature and the implication this resulted from ineffective management. A key challenge was addressing this pressure which, with further incident, may have resulted in enforcement action with associated loss of revenue and reputation.