ABSTRACT
In recent years, production of oil and gas from shale formations has multiplied and now contributes significantly to oil and gas supply. This type of unconventional production differs from historical conventional approaches, with far reaching consequences for asset integrity management. The present paper outlines corrosion threats associated with shale development, including acidizing, fracing, flowback, CO2 and H2S in produced fluids and artificial lift. Usually little detailed information about corrosive exposure is available upfront. The production mode contributes to complex and highly variable environmental conditions. Corrosion cracking and weight loss corrosion of well completion materials are known to have occurred. Whereas classical asset integrity management is usually rolled out over many years, the typical timescale in shale production ranges from just months to a few years, driving low-cost, quick earn-back scenarios. This paper discussed the consequences for materials selection and corrosion control.
INTRODUCTION
The United States has abundant natural gas resources that play a major role supplying energy to homes and businesses. Data for 2017 collected by the U.S. Energy Information Administration (EIA) showed that petroleum and natural gas supplies approximately 66% of the nation’s energy, with natural gas alone delivering about 26%.1 Shale gas resources extend across the lower 48 U.S. states, with an estimated potential of 324 trillion cubic feet.2 However, development of these shale-based resources has also generated numerous technical challenges related to well integrity.
The management of corrosion in downhole environments is a serious challenge for the oil and gas industry in general. Downhole conditions, mainly pressure and temperature, can change dramatically over operating life, especially in the first several months, as the hydrocarbon resource depletes. The chemistry, and volume, of flowback/produced water after hydraulic fracturing will change. Although water is expected to condense at some point along tubing for gas wells, formation water may appear only later in the production life, increasing water cut and bringing additional issues related to water wetting, scaling and under-deposit corrosion. Wells may require acidizing or artificial lift to maximize production, changing fluid compositions and altering the nature of the corrosion threat.
