Field Development and Productivity Improvement Offshore Mexico

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 121928, ’Field Development and Productivity Improvement in Offshore Mexico: An Engineering and Lab oratory Synergistic Approach to Carbonate Fracture Acidizing,’ by Antonio Inda and Octavio Steffani, Pemex, and Eduardo Soriano and Fernando Robles, Halliburton, originally prepared for the 2009 SPE European Formation Damage Conference, Scheveningen, The Netherlands, 27-29 May. The marine light-crude project offshore Mexico is a group of 12 oil fields 75 km off the coast of southern Mexico. The fields have been under development since 2003, are high-temperature carbonate formations producing gas and condensate with permeability that ranges from 1 to 6 md, and are naturally fractured. These fields were experiencing considerable drawdown, which slowed down the return on investment and, in one case, could have led potentially to well abandonment. Established practice dictates that carbonate formations in Mexico are treated best by matrix stimulation rather than fracture-stimulation techniques. The full-length paper demonstrates the effective implementation of a production-optimization design and execution methodology that has translated into productivity increase. Introduction The use of various fracturing methods for stimulation of wells has become a common procedure in the oil and gas industry. Fracture treatments are performed on wells with varying potential to help increase production and reduce the pressure drop on the formation face. Many hydrocarbon-bearing carbonate formations are routinely stimulated by fracture acidizing, and the use of fracture acidizing to enhance the production of carbonate formations continues to be an effective process. To achieve a successful fracture-acidizing treatment, three fundamental issues must be addressed: (1) reactivity control, (2) fluid-loss control, and (3) conductivity generation. Stimulation Challenges Most of the wells in Field A are producing in low-permeability formations ranging from 1 to 50 md. Bottomhole static temperatures (BHSTs) in these wells are often above 300°F. This high temperature enhances acid reactivity and limits penetration into the formation. Established practice dictates that carbonate formations in offshore Mexico are best treated by matrix stimulation rather than fracture-stimulation techniques. This has been established and practiced during the last 20 years of development of fields offshore Mexico on the basis of previous formations being high-permeability carbonates ranging from 100 to 5,000 md. Traditional acid-stimulation jobs in this area were mixtures of solvents/hydrochloric acid (HCl)/organic blends, designed to overcome sludge precipitation and high BHST as a way to distribute acid along the producing intervals. Often, viscosified acids are used as diverter systems with some regular success; however, high reservoir pressure in these fields limit the pumping rates most of the time. Recently, an acid-fracturing campaign started in these fields reported outstanding results and is described in the full-length paper.