Download 001.0 Intro to Sampling PDF

Title001.0 Intro to Sampling
TagsPetroleum Reservoir Petroleum Phase (Matter) Gases
File Size187.3 KB
Total Pages11
Table of Contents
                            Main Contents Page
INTRODUCTION TO SAMPLING
	Sampling Objectives
	Applications of Fluid Analysis Data
	Factors affecting Representative Sampling
	Selecting a Sampling Method
	Bottomhole Sampling
	Surface Sampling
                        
Document Text Contents
Page 1

Introduction to Sampling 1.0 Page 1

Revision 4



Introduction to Sampling Section

This training section is divided into the following topics:



Sampling Objectives

Applications of Fluid Analysis Data

Factors affecting Representative Sampling

Selecting a Sampling Method

Bottomhole Sampling

Surface Sampling




Sampling Objectives

Ideally, the aim of reservoir fluid sampling is to provide the PVT laboratories with small
volumes of fluids under pressure which would, either directly or after recombination,
lead to a sample which is representative of the overall hydrocarbon fluid that fills the
pores of the formation. Coring and logging programs can normally continue throughout
the development of a reservoir because data obtained from the last well is often of equal
value to that obtained from the first. Unfortunately, this is not the case for reservoir
fluids. Due to the change in phase behaviour that occurs once the pressure in the
formation reaches the saturation pressure, sampling should be performed at the very
earliest stage of the field’s production history and preferably before the downhole
average pressure falls below its initial value Pi. This condition has best chance of being
satisfied while testing exploration and appraisal wells, which by definition, are the first
wells to penetrate hydrocarbon deposits and are normally only produced for a limited
period of time.

Experience from the Beryl field, a giant field in the North Sea, underlines the importance
of a thorough evaluation of PVT properties. In that case, initial plans to construct a
platform and the associated production facilities were based on the fluid properties of
samples recovered from the first two wells. These plans had to be changed, at
considerable cost, when further evidence showed that the reservoir oil was much more
volatile than originally anticipated1.

Since erroneous reservoir fluid data can be so costly to the operator it is clear that both
the sampling and analysis must be conducted with the utmost care. Sampling is probably
the most delicate of field operations since it requires not only solid experience in open
hole logging or well testing, but a also a thorough understanding of reservoir
engineering, and well behaviour problems.

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