Spinners Run While Perforating
Authors: Davies J. , van Dillewijn J. , Herve X. , Kusaka K. 
Published: December 2007

A novel technique which offers scope for significant rig time savings has been successfully applied in the Brent Field in the UKCS. This technique involves running a memory production logging string containing spinners and pressure/temperature gauges in conjunction with electric line perforating guns. It has been applied in three Brent wells to date (two producers and one injector). In each case MPLT data was acquired both before and directly after firing the guns, without having to pull out of hole. Full memory data recovery was achieved for all runs; data quality was comparable to that of typical electric line PLT's.

The three runs were performed with varying applications in mind:determine the extent of crossflow prior to obtaining a fluid sample,perform leak investigations on recently set Casing patches anddetermine gross production/injection splits.

Each of these applications was carried out successfully. In addition, six to eight hours of rig time were saved in each case. This confirms the potential for significant cost/time savings, particularly if the technique is extended to coiled tubing operations. Similarly, the technique could be extended to include other PLT sensors and/or fluid sampling tools. Although this technique is unlikely to replace the logging of normal electric line PLT's, we believe that it holds great promise for fit for purpose production logging applications which don't require real time intervention.

Introduction

By applying tried and tested technology in a novel fashion, significant rig time savings can be achieved. An example of this is the application of standard memory production logging technology while perforating. Recent experience in the Brent Field in the UKCS has shown that it is feasible to run both memory pressure/temperature gauges and memory spinners below perforating guns and thus obtain MPLT information before and after perforating without pulling out of hole. By combining the surveys with the perforating operations, rig time can be saved without sacrificing data quality. In this paper we will discuss the technical details of the tools used and outline the results of the three operations performed to date.

Tool specifications

A schematic of the MPLT tool string as run in Brent is shown in Figure 1. Combined tools are, from the bottom: fullbore spinner (FBS), centraliser, in-line spinner (CFS), pressure/temperature sonde (SPLS), memory downhole recorder (MDR), adapter, sapphire crystal gauge (SLSR) and shock absorber. Tool selection was based on two criteria: robustness and reliability. Robustness is required because the tools are exposed to the shock of the gun detonation. Reliability is particularly important as, being memory tools, there is no means of knowing whether or not they have functioned properly until they are recovered at surface. It is for this reason that, in order to increase the chances of full data recovery, two spinners and two pressure/temperature gauges were run in tandem.

The FBS and CFS that were used are identical to the spinners used in field-proven electric line PLT strings. There are several sizes available to cater for different casing sizes and flowrates. The specifications of the spinners used can be found in Table 1. The SPLS and SLSR gauges are two different types of pressure/temperature gauges. The SPLS consists of a Quartzdyne sensor, and is run in conjunction with the MDR (see below). The SLSR consists of a sapphire crystal sensor, and is a stand alone memory gauge (i.e. with its own recording facility). It is run both on slick line and during DST/TCP operations (in a gauge carrier above or below a packer). Specifications of both gauges are summarised in Table 2. P. 535^