Document

Predicting and managing evaporative halite precipitation and liquid loading : case study from a gas field in Oman.

Other titles
تنبؤ وإدارة ترسب ملح كلوريد الصوديوم وتراكم السوائل في آبار الغاز : دراسة حالة في حقل غاز في سلطنة عمان
Publisher
Sultan Qaboos University.
Gregorian
2023
Language
English
Subject
English abstract
Halite precipitation and liquid loading are considered as perilous threats to gas wells impacting their productivity at the end of the wells' production lifetime. Accurate prediction of the start of these problems is very essential to guarantee a proper mitigating or managing plans. Predicting liquid loading problem is very mature and this issue is proved to be managed by reducing the size of the tubing (i.e. installing velocity string (VS)). In contrast, the prediction of the onset of halite precipitation is still lacking sufficient research and the existing approaches are only applicable in well level and yet not adequately validated. Additionally, the current deployed halite management measures are inefficient and not cost effective. There are many gas wells in PDO company suffering from halite precipitation, and various actions have been taken to mitigate and manage this problem. A more recently identified possibility is utilizing smaller completion size (velocity string) to mitigate / remove halite problem, which at the same time comes with benefit of gas well deliquification. However, more study is required to confirm the suitability and efficiency of this possible solution. This study aims to develop a general and replicable model, using halite envelope, to predict the halite precipitation issue in a gas field in Oman. To achieve this objective, thirty halite envelopes for thirty different gas wells, known to have experienced halite precipitation problem, were simulated. The simulation showed that, there is significant variation in the size and shape of the halite envelope of the different wells and therefore the concept of constructing a single envelope for the whole field turned out to be infeasible. However, grouping halite envelopes of different wells based on their inflow resistance, followed by constructing a halite envelope model for each group was proved to be a powerful tool for halite prediction. The study also investigated the technical viability and the pros and cons of using velocity string technology as a new approach in managing halite precipitation issue. This was achieved by simulating the halite envelope of few wells assuming different sizes of velocity string are installed, followed by analyzing the halite envelopes and estimating the timing of halite precipitation re-occurrence. The study revealed that using velocity string as a halite remedial technique depends mainly on the rock quality as well as the time of installing the velocity string. Furthermore, the study aims to predict the time of the liquid loading issue of same wells, evaluating the impact of installing velocity string on liquid loading and assess the synergy between halite management and de-liquification by using velocity string. This objective was achieved by estimating the time it takes the selected wells to load-up and then compare the time to liquid loading with the time of halite recurrence when velocity string is installed. The study concluded that generating a synergy between halite management and de-liquefaction using velocity string depends mainly on the rock quality and the size of the installed VS.
Arabic abstract
يعتبر ترسب ملح كلوريد الصوديوم )الهاليت( وتراكم السوائل المنتجة من التهديدات الخطيرة لآبار الغاز التي تؤثر على إنتاجيتها في نهاية عمر إنتاج الآبار. يعد التنبؤ الدقيق ببدء هذه المشكلات أمرا ضروريا للغاية لضمان خطط التخفيف أو الإدارة المناسببة لهذه التهديدات. التنبؤ ببدء مشكلة تراكم السوائل من العمليات التي من الممكن القيام بها بالدقة المناسبة وقد ثبت أن هذه المشكلة تتم إدارتها عن طريق تقليل حجم أنبوب الانتاج في المقابل لا يزال التنبؤ ببدء ترسب ملح كوليد الصوديوم يفتقر ألى البحث الكافي والنهج الحالية قابلة للتطبيق فقط في مستوى البئر ولم يتم التحقق من صحتها بشكل كاف.
Category
Theses and Dissertations