Cementing, Perforating, and Fracturing Using Coiled Tubing
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 138798, ’Cementing, Perforating and Fracturing Using Coiled Tubing: Rigless Completion Technique Developed for a Marginal Field in Peru,’ by V. Salazar, BJ Services; V. de la Rosa, Sapet Development; and J. Gomez, SPE, and J. Quintana, BJ Services, originally prepared for the 2010 SPE Latin American and Caribbean Petroleum Engineering Conference, Lima, Peru, 1-3 December. The paper has not been peer reviewed.

The full-length paper presents a new rigless completion technique involving plug and abandonment of the lower zones, followed by cementing, perforating, and fracture stimulating the new zone using only coiled tubing (CT) for intervention. The technique has proved to be an economically viable way to return to life the first 18 wells completed.

Introduction

The Talara basin, on the northeast Peruvian coast, holds several very mature fields producing from low-permeability, very-complex sandstones. The original target zones were at more than 4,000 ft in the Parinas, Mogollon, and Basal Salina formations. In most of the blocks, these original targets are very depleted and well interventions usually are not economical. For this reason, other reservoir formations that were not considered as viable targets now are considered of interest for recompletion. In this analysis, the upper formations considered were Verdun, Helico, and Talara, which hold oil reserves that can be produced. However, in Blocks 6 and 7 of the Talara basin, the wells are deeper than this formation, most of them having been drilled in the 1940s, and were cemented with the cement top below these formations. Considering the reservoir conditions of low permeability and low pressure, the wells need to be fractured hydraulically to be produced.

Because these wells do not have hydraulic isolation to surface from the formations to be recompleted, the challenge is to be able to provide cement isolation to the reservoirs to be completed with hydraulic fracturing. The fields are very mature, and the expected production is quite low, thus this recompletion process could be beyond the economical limit, so the challenge is that this recompletion has to be deployed at the minimum possible cost. If successful, hundreds of opportunities will be available for this type of recompletion. The full-length paper is based mainly on experience in Talara. The approach used was to perforate, deploy cement isolation, and fracture stimulate in a simple rigless operation with the minimum amount of equipment and people.

Recompletion Overview

After analyzing different options, the approach selected was to use a light CT unit to perforate and to deploy cement isolation rings above and below the fractured zone. The next step was to perforate and fracture the Verdun formation. This procedure was to be performed in one or several stages if required, depending on the thickness of the reservoir. The perforations were achieved using the sand-jet technique. Because it has been impossible to circulate through the noncemented section, the cement isolation was placed by squeezing cement through the perforations.