An Economical Method of Rapid Reservoir Testing
Authors: Porteous W.R. , Maier L.F. , Clark J.W. 
Published: December 2007

PORTEOUS, W.R., JUNIOR MEMBER AIME, CIA. HALLIBURTON DE CEMENTACION Y FOMENTO, MARACAIBO, VENEZUELA MAIER, L.F., JUNIOR MEMBER AIME, HALLIBURTON OIL WELL CEMENTING CO. LTD., CALGARY, ALTA. CLARK, J.W., HALLIBURTON OIL WELL CEMENTING CO. LTD., RED DEER, ALTA.

A tool designed for formation sampling during drilling has been placed in Canadian field operations for over two years. Relatively large fluid samples are recovered and a formation pressure build-up obtained without retrieving the drill pipe. This paper discusses the mechanical operation of the tool as well as the characteristics of sample recoveries and pressure data. Typical examples are given. Qualitative reservoir information may be obtained to assist the operator in further evaluation and completion operations. Special applications include aid in the location of gas-oil and oil-water contacts, the calculation of potentiometric surfaces and the determination of reservoir continuity or segregation. An economic comparison with conventional drill-stem testing is made to illustrate the possible extent of savings. A summary of operations is given, describing the tool's performance and the results achieved.

Introduction

The Continuous Retrievable (CR) Sampler is a tool designed for retrieving large samples of reservoir fluid as well as recording a pressure build-up which approaches or reaches reservoir pressure. The entire operation is performed with the drill pipe in the hole. This is accomplished by incorporating the packer as an integral part of the drilling string, and recovering the formation fluids and pressure data by means of a wireline retrievable reservoir. The tool has been in operation in Canada for over two years, and during this time its use has constantly expanded. This rapid industry acceptance has been due to the low cost and time-saving operation of this aid for formation evaluation, as well as the excellent mechanical performance record of the tool. Other recognized advantages include the sampling of a formation a short time after it has been penetrated by the bit, and the ability to sample at any time during the drilling operation with both the drill pipe and hole full of fluid. The purpose of this paper is to describe the mechanical operation of the tool and to discuss the results obtained. Several special applications will be suggested.

Mechanical Operation

The CR Sampler consists of two distinct assemblies, as illustrated in Fig. 1the packer assembly, which is an integral component of the drilling string; andthe sampler assembly, which is dropped down the drill pipe from the surface whenever the operator desires to sample the formation.

The packer element, which is located about 4 ft above the bottom of the bit, consists of three separate components. An inflatable cylindrical bladder is mounted on the packer assembly. Over the bladder is placed a tough rayon sleeve, on which the outer inflatable rubber packer (reinforced with steel mesh) is mounted. The packer element is inflated by applying internal pressure in the drill pipe. This may be done only after the sampler assembly has been dropped into the packer assembly. Seal cups on the sampler assembly are designed to retain drill-pipe pressure within the tool, allowing a sliding sleeve valve in the packer assembly to be opened when pressure is applied. Opening the sleeve valve allows the pressure to be transmitted through pressure ports to the bladder. This valve is pressure-balanced and held closed by a strong spring during drilling operations. The packer assembly has an outside diameter of 6 3/4 in. and is approximately 14-ft long.

JPT

P. 957^