Combined Smart-Chemical System and Real-Time Temperature Sensing: A Case Study
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 154387, ’A New Methodology for Stimulation of a High-Water-Cut Horizontal Oil Well Through the Combination of a Smart-Chemical System With Real- Time Temperature Sensing: A Case Study of South Umm Gudair Field, PZ Kuwait,’ by A. Al-Najim and A. Zahedi, Chevron; T. Al-Khonaini and A.I. Al-Sharqawi, Kuwait Gulf Oil; and P.M.J. Tardy, SPE, A.R. Adil, SPE, I. Nugraha, P. Ramondenc, SPE, and F.S. Al-Hadyani, Schlumberger, prepared for the 2012 SPE/ICoTA Coiled Tubing & Well Intervention Conference & Exhibition, The Woodlands, Texas, 27-28 March. The paper has not been peer reviewed.

A case study is presented of a matrix-acidizing treatment whereby the combination of a “smart fluid” in a stimulation treatment pumped through coiled-tubing (CT) with real-time distributed-temperature-sensing (DTS) technology helped improve the real-time decision process of fluid placement, temporary-plugging placement, and treatment-efficiency evaluation. To facilitate on-site decision making, a temperature-inversion technique was used to translate the actual-temperature profiles into fluid-invasion profiles across the horizontal openhole section of the well. Also, full-scale acid-placement and thermal modeling is proposed to perform in-depth post-treatment evaluation.

Introduction

The South Umm Gudair field, discovered in 1966, is in the neutral zone between Kuwait and Saudi Arabia. It produces mainly from the Ratawi oolite, a Lower Cretaceous reservoir, by a water-drive mechanism. The drilling-and-completion strategy has evolved from simple vertical wells to horizontal wells to maximize reservoir contact and to minimize the producing water cut. Over time, an increase in the water cut is inevitable. The task of performing an efficient stimulation, which is required for improving the well’s production, becomes more challenging without knowledge of, and control over, where the acid will flow during the treatment, with no means of avoiding stimulation of the water zones.

Real-time DTS had not been used to evaluate the effectiveness of temporary isolation and subsequent stimulation; however, real-time DTS has been used with matrix-acidizing treatments to evaluate zonal coverage. The approach presented here enables engineers to deal with the uncertainty of predicting fluid placement along the well and to act in real time following the interpretation of the DTS logs recorded during the treatment.

Background

The horizontal well produces oil from a formation with porosity in the 15±5% range. It produces from an openhole section 2720 m deep, with the casing shoe (CS) at a measured depth (MD) of 2887 m and a total depth (TD) of 3343 m.

The well was drilled and completed in August 2010. A swabbing test during the completion indicated poor productivity, with water being the dominant phase. Therefore, chemical stimulation was performed. During the stimulation design, the decision was made to split the hole section into two parts—Zone 1 and Zone 2. Zone 1, with relatively higher resistivity and heterogeneity, was considered the primary zone of interest. Zone 2, with lower resistivity and higher porosity, was suspected to contribute water. It then was decided to exclude Zone 2 from chemical stimulation by temporarily plugging it with a smart fluid.