Solving Excessive Water Production in a Long Horizontal Open Hole

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 113700, "Solving Excessive Water Production in a Prolific Long Horizontal Open Hole Drilled in a Naturally Fractured Carbonate Reservoir," by Stephen Lightford, SPE, Halliburton, and Enzo Pitoni, Giovanni Burrafato, and Claudia Porretta Serapiglia, Eni E&P, originally prepared for the 2008 SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition, The Woodlands, Texas, 1-2 April. The paper has not been peer reviewed. A case history is presented of a successful operation to reduce excessive water production in a horizontal well drilled through a naturally fractured carbonate reservoir. Because the well was completed with a 940-m horizontal openhole section, there was no practical means of selectively isolating sections of the open hole. A treatment was performed using a sealant that would set up only in the presence of water. The full-length paper describes the philosophy behind the treatment design, the testing of the sealant, the placement procedure, and subsequent well performance. Introduction The case study is taken from a field in southern Italy that lies within a mountainous national-park area and is classified currently as the largest producing onshore field in continental Europe. Wells in the field are very-high-producing wells from a naturally fractured carbonate reservoir at approximately 3500 m true vertical depth (TVD). Permeability is difficult to predict because it is dependent on natural fracturing, which results in a wide range of production rates from individual wells. Because the field is in a national park, development is strictly controlled and wellsites are limited to fit in with the environment. Very strict governmental controls on the operations in the field help ensure that work is minimized to what is absolutely necessary. Planning to move a rig onto the wellsite normally is a long process to obtain the required authorizations and is particularly expensive because of the mountainous terrain. Rigless interventions and use of coiled tubing (CT) in the field have become widespread. When a naturally flowing well suddenly starts producing excess water, and oil production is lost because the well is killed by increased hydrostatic pressure; there is an intense commercial driver to attempt to resolve the problem with a rigless intervention. This situation offers an opportunity to use newer techniques because the commercial benefits of a successful job make the amount of risk acceptable to an operator willing to resolve the problem. This scenario provides a rare opportunity to use untried methods, as was the case in the job described in the full-length paper.