Abstract

The "Unified test protocol for laboratory formation damage assessments" consists of functional procedures that attempt to standardise formation damage service projects. Setting functional requirements was preferred above detailed instructions with respect to laboratory work processes and the handling of laboratory equipment.

In order to assess the formation damage potential of a fluid for drilling or well operations, three sections of the protocol need to be accomplished. These are respectively: "Information", "Simulation" and "Analysis".

This paper presents the three sections of the unified protocol and discusses the effect of the functional approach. Special emphasis is put on a distinction between well fluids that experience dynamic and static filtration regimes, as these require different ways of simulating fluid applications to the rock sample. To provide engineering parameters relevant at field scale and to identify the full range of potential formation damage mechanisms that may affect the reservoir, analyses on "centimeter", "millimeter" and "micrometer" scale are suggested.

Minimum requirements to upscale formation damage measurements to field scale are presented. We also present an option for full scope "diagnostic" formation damage assessments.

Applications of numerical models that have been suggested in earlier research yield "return permeability", "filtrate invasion depth", "lab skin", "efficiency of flow" and "loss of revenue" as parameters to benchmark the formation damage of well fluids.

Introduction

Prevention of formation damage through fluids used for drilling and well operations provides one of the key elements for the economic success of oil- and gasfield developments. It affects not only commercial interests, but also the total quality of the production process. Hence, it comes along with increased up-time and process reliability, as well as a reduction in total HES-related risks. The latter is related to reduced exposure of staff and environment because the need for stimulation/workover operations on damaged wells or even the drilling of additional wells to exploit the full reservoir potential is reduced.

The work reported in this paper is part of a research initiative supported by the EU-commission within the 5th framework research and technical development programme. This research initiative, termed "Well Productivity 2002", short "WP2002", aims to deliver development strategies and new products to drill, complete and maintain wellbores in such a manner that the optimum delivery potential of a hydrocarbon reservoir is protected.

As one task to approach the project objectives, a work package was defined to develop cost-effective laboratory and field diagnostic methods to characterise and quantify formation damage. The particular objectives of this work package were among other to:

  1. Establish minimum equipment requirements for simple "screening-type" formation damage assessments.

  2. Demonstrate a viable and unified set of laboratory test protocols for "screening" and "diagnostic"-type tests.

We present below a test protocol that attempts to satisfy these objectives. This protocol is based on a functional approach rather than detailed requirements. Suggestions to satisfy functional requirements in practice are given. The primary thought when developing the protocol was to structure the communication between user and supplier of the service project and to link field and laboratory closer together.

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