The Burst Cause and Prevention of Steam Injection Pipeline

Abstract

Abstract The paper presents examples and analyses of the burst failure of steam injection pipeline. It suggests that the main burst cause of high-pressure injection pipeline is partial corrosion. The paper also provides preliminary analysis of the causes of partial corrosion and puts forth specific measures to control partial corrosion and to prevent pipeline burst. Foreword In last 3 years four bursts have occurred in three oilfields with a total length of 710m steam injection pipelines broken. This results much damage to the surrounding buildings and farmlands on the burst spot. Pipelines flung broke the high voltage poles in a distance of about 100m when burst occurred. According to the rough estimates, the direct economic loss reached 20 million yuan RB. That was a threat to the personal safety of the working people in heavy oil production and steam injection system. After the bursts the engineering and technical personnel and experts concerned were be organized to investigate end analyse the burst causes. Based on the observation of the appearance of the burst pipelines and the examination to the quality of the pipelines material and water used for steam generators, a comprehensive analysis of all related information was performed with references of the relevant experiences from the other industries. Thus a conclusion was reached, that the burst was caused by partial corrosion of the tubular in wall. While the partial corrosion was mostly caused by the poor standard water and the low resistance to corrosion of the material. The important way to control corrosion and prevent burst failure is to improve water processing and adopt corrosion-resistant low carbon alloy steel material. Brief Introduction to the Operation and Failure of the Steam Injection Pipeline 1. Material of the Steam Injection Pipeline The caliber of the main transportation pipeline is 127x14mm and the caliber of the well outlet pipe is 89x11mm. 20G seamless steel pipe is adopted in practical operation. The quality of this kind of material is shown in Table 1. 2. Operation of Steam Injection Pipeline The following working parameters are designed for the steam injection pipeline: highest operation pressure, 18.3MPa; highest operating temperature, 357 C; the practical steam injection pressure is 9 to 17Mpa with a corresponding saturated wet steam temperature of 305 C to 350 C and a steam quality of less then 80%. Water used in the steam generator comes from underground water, Yellow River water and the mixture of the two. Except for the higher oxygen content and lower pH value, the other specifications are identical with standard water quality set by SY0027-94 and API RP11T. 3. Brief Introduction of the Four Burst Failures of Steam Injection Pipeline No. 10 steam injection station was put into operation on 15, April, 1994. On 28, May, 1994 the outlet pipeline burst. About 147m pipeline of the 127x14mm collapsed into 10 segments. At that time, the injection pressure was 16.5Mpa, temperature 341 C, wet steam quality 61%, injection velocity 23 t/h. The steam injection pipeline of No. 1 steam injection station was completed and put into operation on 17, July, 1993. Burst occurred on 10, June, 1994, after igniting steam generator only 20 minutes. Which broke pipeline of 138.3 meters (among which 128.0m pipeline of 127x14mm, and 11.7m of 89x11mm) into 13 segments. The steam injection then was conducted with a pressure of 14.3Mpa, temperature of 327 C, injection rate of 21 t/h, and saturated wet steam quality was 53%. The steam injection pipeline in north of No. 2 station was put into operation on 22, November 1994. Burst happened on 25, March 1995, which broke 107 meters of pipeline. Steam was then injected with a pressure of 15.5MPa, a temperature of 340 C, a quality of 49% and an injection velocity of 14t/h. The 127x14mm pipeline of No.s2 steam injection station was put into operation in November 1986. It burst on 30, December 1995, the east branch of the T-junction in 100 meters north of No.s2 station. A total length of 400 meters of the pipeline was broken into 22 segments. At that time, the injection pressure was 13.5Mpa; and temperature 330 C, quality 71%, injection velocity 9.8t/h. 4. Property Analysis of the Burst Pipe Material Chemical Composition Analysis of the Pipe Material Chemical composition analysis of the burst pipes (of No. 10 injection station, No. 1 station and No.s2 station) shows that the chemical composition of the burst pipe materials is in agreement with that of st45.8 steel (as in table 1). Mechanical Test of the Pipe Material Respective sample materials were taken from the corroded part and uncorroded part along the same pipe to analyze the effect of corrosion on the mechanical property of pipe materials. Various mechanical tests were performed and results were compared. P. 51^