炭素隔離プロジェクトにおける坑井完整性保証のためのセメントシースCO2漏洩率予測の実践的アプローチ

Unofficial AI-generated summary based on the public title and abstract. Not an official translation.

🔬研究者:セメント劣化・アニュラス流を簡便な解析モデルで漏洩率に結びつける枠組みを、CCS封じ込め研究に応用できる。

🏢実務担当者:CCS事業者は坑井状態ではなくアニュラス領域に着目した漏洩リスク評価を事業設計・モニタリングに組み込める。

🏛政策担当者:CCSの長期貯留責任や漏洩基準設定において、定量化された漏洩率評価手法を規制設計に参照できる。

Concerns in geological carbon sequestration projects center on potential leakage from the storage complex that could impact freshwater aquifers. This work develops a method to estimate probable carbon dioxide (CO2) leakage rates through cement sheaths, providing a quantifiable basis for wellbore integrity assurance. Initially developed through the Anadarko Basin Southwest Regional Partnership, this work advances that approach through a Delaware Basin CarbonSAFE Phase II project. The refined method enables CO2 leakage estimation through bulk cement and micro-annuli. Storage integrity in carbon sequestration encompasses both caprock and wellbore, with the latter posing complex challenges. Legacy wells, though properly plugged, remain susceptible to degradation. Cyclic loading over time can compromise annular cement behind casing or liner, creating channels or micro-annuli through which CO2 plumes may migrate. This work is built upon laboratory-derived American Petroleum Institute (API) Class C and H cement permeability, rebuilding the leakage quantification concept from petroleum-engineering principles. Flow through degraded cement is modeled as porous media using Darcy's law. Flow through micro-annuli is treated as annular flow in boreholes, applying narrow-slot approximation for practicality. A case study was conducted on three legacy wells in the Delaware Basin, all located within two miles of the CO2 injector. The operation targets an annual injection of 1.5 million tonnes CO2 into the Devonian zone. Wells IN1 and IN2 are inactive, whereas Well PL1 is permanently plugged. Superficial assessment would flag the inactive wells as primary leakage conduits once the CO2 plume arrives in their region downhole in a certain timeframe. However, none of these wells were ever perforated in the Devonian formation, suggesting potentially reliable containment. The predictive method yielded contrasting results. Well IN2 showed a probable total CO2 leakage rate of 1.6 tonnes/year—approximately 0.0001% of the annual injection rate. Well PL1 was estimated at 1.0 tonne/year, and Well IN1 at 0.67 tonnes/year. Two key conclusions emerge. First, well status alone does not dictate containment risk. Plugs seal the main borehole trajectory but do not address the primary concern of the annular region segregating borehole from formation. Second, the estimated rates provide quantifiable insight into storage complex integrity. Industry rule-of-thumb considers annual leakage exceeding 1% of injected mass as ineffective sequestration; all three wells fall orders of magnitude below this threshold. This work delivers more than leakage rates. By applying a predictive, analytically simple approach grounded in Darcy's law, annular flow concepts, and lab-based cement permeability estimation against the industrial UK Oil and Gas Industry Association Limited (OGUK) baseline, it provides a framework for classifying wellbore integrity assurance. When integrated with the common reservoir properties analyses nowadays, this enables a thorough assessment of long-term storage system sustainability, extending understanding from mere quantification to holistic containment viability over decades or centuries.

• semanticscholar https://doi.org/10.2118/234011-msfirst seen 2026-10-18 05:30:45 · last seen 2026-10-22 05:50:35