As oil and gas becomes more difficult to find and wells are drilled deeper the well bottom hole temperature increases. The temperatures of deep wells can be as high as 230°C. There are a limited number of oil soluble corrosion inhibitors that work well in such systems. In this paper we report the development of a new water based corrosion inhibitor that works at high temperature and can be injected using a capillary string. A new water soluble corrosion inhibitor has many advantages such as greater partitioning in the water phase, higher flash point and higher reportable quantities (RQ) if a spill occurs than the oil soluble counterparts. In this paper the laboratory studies on new high temperature water soluble corrosion inhibitor are reported. The performance of this corrosion inhibitor in a field trial is also reported. Wherever possible the water soluble corrosion inhibitor will be compared with a standard high temperature oil soluble corrosion inhibitor.
As shallow onshore and offshore oil fields mature, new discoveries will occur in deeper reservoirs with higher temperatures and more severe materials problems. The challenges presented by ultra high pressure and temperature wells (ultra-HPHT) has been described by Zeringue.1 As described in the article, there are several material issues that are involved in ultra-HPHT well technology. There are both technical concerns and lead time concerns involving the use of nickel based alloys for this application.1 Carbon steel in conjunction with corrosion inhibitors has been used in several wells above 150 °C.2-5 The inhibitors used in these applications were formulated in a hydrocarbon solvent system. An inhibitor that is primarily formulated in water will transport more easily to low spots in the line and preferentially partition to the water phase. The water based corrosion inhibitor will also have a higher flash point and hence be safer to handle. In this paper the development of water based corrosion inhibitors that have similar/better corrosion inhibition performance to a standard high temperature corrosion inhibitor formulated in a hydrocarbon solvent, with superior secondary properties, and environmental and handling advantages is described.
Corrosion inhibitor tests were performed in a variety of devices to ensure that the corrosion inhibitors are compared in a large number of situations with different ways that corrosive fluids contact carbon steel. The test methodologies included, the wheel bomb (WB), the high speed autoclave (HSAT) apparatus, and the jet impingement (JI) device. The first set of WB tests measured the film persistency of the corrosion inhibitor. In this test 1018 carbon steel coupons were filmed with corrosion inhibitor at different concentration of inhibitors in soda bottles under saturated CO2 and 180 °F (82 °C) conditions for 1 hour. The coupons were then rinsed with deionized water and transferred to the wheel bomb in inhibitorfree brine. The tests were performed at 350 °F (177 °C). The tests were performed with carbon dioxide gas at a pressure of 100 psi (687 kPa). The composition of brine used in the test is shown in Table 1.
