Assessment of Asphaltene Production on Fracture Aperture During Heavy Oil Recovery

Öz

During reservoir engineering analysis, the assessment of the possibility of asphaltene precipitation and corresponding heavy oil recovery with economic losses is carried out before any thermal operation. Since, asphaltene precipitation reduces oil production, both by plugging the pipeline network and by decreasing the effective permeability in the reservoir. In this study, to analyze this phenomenon, three steam injection experiments; only-steam, steam-CO2, and steam-n-C4H10 at 1:1,29 volumetric ratios were carried out in limestone cores saturated with a 12,4 °API heavy crude oil. After each experiment produced oil asphaltene content was measured. Further, to determine the asphaltene effect on the fracture apertures and permeability, improved cubic law (ICL) equation was used to determine the equivalent fracture aperture change during the experiments. Equivalent fracture apertures were calculated analytically. An initial observation, made for only the steam injection experiment, was a decline in asphaltene levels present in the producing oil. Asphaltene levels gradually increased as the effects of steam progressed. When CO2 was added to steam the asphaltene content of the produced oil was increased. Nevertheless, the asphaltene content increased in produced oil was not changed the fracture permeability and equivalent fracture aperture considerably. In contrast, when n-C4H10 was injected with steam concurrently, the asphaltene levels gradually elevated above the starting value. However, in the further injection period, asphaltene content in the produced oil was lowered below the starting value as the injection progressed. This indicated that a partial upgrading of the asphaltene in the rock matrix by causing improvement in the equivalent fracture apertures.

Anahtar Kelimeler

• Steam Injection
• Hydrocarbon Gas
• Asphaltene Content
• In-situ Upgrading
• Inproved Cubic Law
• Equivalent Fracture Aperture

Assessment of Asphaltene Production on Fracture Aperture During Heavy Oil Recovery

Öz

Rezervuar mühendisliği analizi yaparken herhangi bir termal uygulama öncesinde asfalt çökelme olasılığı ve oluşabilecek ekonomik kayıpların tahlili yapılmalıdır. Asfalt çökelmesi hem üretim kuyusundaki boruları hem de boru hattı ağına bağlı boruları tıkayarak, ayrıca rezervuarın etkili geçirgenliğini düşürerek petrol üretimini azaltır. Bu çalışmada, karşılaşılan durumu analiz etmek için üç buhar enjeksiyon deneyi; sadece buhar, 1:1,29 hacimsel oranlarında buhar-CO2 ve buhar-n-C4H10 testleri, 12,4 °API ağır ham petrol ile doyurulmuş kireçtaşı karotlarda gerçekleştirilmiştir. Üretilen petrolün asfalt miktarı her deneyden sonra ölçülmüştür. Daha sonra, eşdeğer çatlak aralıkları ve geçirgenlikler üzerindeki asfalt etkisini gözlemlemek için; geliştirilmiş kübik yasası (ICL) denklemi kullanılmıştır. Her karot deneyi için eşdeğer çatlak aralıkları analitik olarak hesaplanmıştır. Sadece buhar enjeksiyon deneyi için yapılan ilk gözlem, üretilen petrolde bulunan asfalt seviyelerindeki düşüş olmuştur. Buharın etkileri ilerledikçe asfalt seviyeleri giderek artmıştır. Buhara CO2 ilave edildiğinde üretilen petroldeki asfalt içeriği, artmıştır. Bununla birlikte, sadece buhar deneyindekine karşılık gelen asfalt birikmesi ölçüsü, çatlak geçirgenliğini ve eşdeğer çatlak aralığını önemli ölçüde değiştirmemiştir. Buna karşılık, n-C4H10 aynı anda buharla enjekte edildiğinde, asfalt seviyeleri kademeli olarak başlangıç değerinin üzerine çıkmıştır. İlaveten, daha sonraki enjeksiyon döneminde, üretilen petroldeki asfalt içeriği, enjeksiyon ilerledikçe başlangıç değerinin altına düşmüştür. Bu da kaya matrisindeki asfaltın, eşdeğer çatlak aralıklarında genişlemeye neden olarak kısmen iyileştiğini göstermiştir.

Anahtar Kelimeler

• Buhar Enjeksiyonu
• Hidrokarbon Gazı
• Asfalt Miktarı
• Yerinde İyileştirme
• Geliştirilmiş Kübik Yasası
• Eşdeğer Çatlak Aralığı

Kaynakça

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