Oil Casing Composition for CO2 and Microbial Corrosion Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing oil casings do not provide adequate resistance to both CO2 and microbial corrosion, particularly from sulfate-reducing bacteria (SRB) and saprophytic bacteria (TGB), failing to meet the high-strength requirements of 110 ksi-125 ksi steel grade needed for deep oil and gas well operations.
Innovation Solution
A high-strength oil casing composition with controlled amounts of Cr, Cu, P, S, and optionally REM, combined with a TMCP manufacturing process, including specific rolling and cooling rates, to enhance corrosion resistance and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high chromium content (12.0-14.0% Cr) is used to improve CO2 corrosion resistance, then CO2 corrosion resistance is improved, but SRB corrosion resistance is not achieved
Solution Approach 1:
The patent combines multiple alloying elements (Cr, Cu, Ni, Mo, Mn, Ti, REM) in specific proportions to create a composite steel material that provides both CO2 corrosion resistance and SRB corrosion resistance simultaneously, rather than relying on a single element like chromium alone
Solution Approach 2:
The patent optimizes the content ranges of multiple alloying elements and controls impurity levels (P≤0.050%, S≤0.010%) to achieve the desired dual corrosion resistance while maintaining 110-125 ksi strength grade requirements
2Strength
If high nickel content (1.5-5.0% Ni) and high chromium content (15.5-18.0% Cr) are used to achieve 110 ksi strength grade, then strength is improved, but SRB corrosion resistance is not achieved
Solution Approach 1:
The patent creates a multi-element alloy system where Cr (1.5-7.0%), Cu (0.3-3.5%), Ni (0.5-3.5%), Mo (0.1-3.5%), and other elements work synergistically to provide both high strength (110-125 ksi) and SRB corrosion resistance, moving beyond simple stainless steel compositions
3Reliability
If high copper content (0.3-3.5% Cu) and optimized chromium content (1.5-7.0% Cr) are used, then SRB and TGB corrosion resistance is achieved, but strength may not reach 110-125 ksi grade
Solution Approach 1:
The patent integrates Cu (0.3-3.5%) for microbial corrosion resistance with Cr (1.5-7.0%), Ni (0.5-3.5%), Mo (0.1-3.5%), Mn (0.10-2.5%), Ti (0.01-0.10%), and other strengthening elements to achieve both high strength (110-125 ksi) and dual corrosion resistance simultaneously
Solution Approach 2:
The patent optimizes the combined effects of multiple alloying elements and their interactions, controlling impurity levels (P≤0.050%, S≤0.010%) to achieve the synergistic effect needed for both high strength and corrosion resistance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves an oil casing with yield strength of ≥758 MPa, full-sized impact energy of ≥80 J, and corrosion resistance to CO2, SRB, and TGB, with average and local corrosion rates below 0.0250 mm/a and 0.0450 mm/a respectively, under simulated well conditions.
Implementation Method 1
a manufacturing method therefor comprising the following steps: S1: smelting and casting molten steel into an ingot, subsequently forging or rolling to obtain a pipe blank; S2: performing heating, heat holding, piercing, continuous-rolling, and stretch reducing or sizing on the pipe blank of step S1
Implementation Method 2
S3: cooling the pierced billet of step S2 to room temperature, obtaining an oil casing
Data Source
AI summary
The present disclosure provides a high-strength oil casing resistant to CO2 and microbial corrosion and a manufacturing method therefor. The oil casing comprises, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass: C: 0.06-0.20%, Cr: 1.5-7.0%, Cu: 0.3-3.5%, P≤0.015, S≤0.007. For the oil casing of the present disclosure, an oil casing with CO2-SRB-TGB corrosion resistance, a yield strength of ≥758 MPa, preferably ≥800 MPa, and a full-sized impact energy at 0° C. of ≥80J, preferably ≥95J can be obtained by controlling the amounts of Cr and Cu added and the contents of impurity elements P and S, optimizing the proportion of chemical elements, and combining TMCP manufacturing process, controlling the rolling temperature, the temperature before cooling and the cooling rate.