في عالم الحفر الاتجاهي، يشير مصطلح "نصف القطر المتوسط" إلى نوع معين من مسار البئر الذي يتميز بـ **معدل انحراف معتدل**. عادةً ما يُعرّف هذا المعدل **بما بين 8 و 12 درجة من التغيير في اتجاه البئر لكل 100 قدم من عمق الحفر**.
لماذا نصف القطر المتوسط مهم؟
توفر آبار نصف القطر المتوسط توازنًا بين **الانحراف المُتحكم به** و **الكفاءة في الحفر**. تُستخدم هذه الآبار بشكل شائع عندما:
تغيير انحراف البئر عند 8° لكل 100 قدم:
يقع تغيير انحراف البئر عند **8 درجات لكل 100 قدم** ضمن النطاق النموذجي لآبار نصف القطر المتوسط. هذا يعني أن البئر سوف يتغير اتجاهه بمقدار 8 درجات لكل 100 قدم يتم حفرها عموديًا.
تصور الانحراف:
تخيل خطًا مستقيمًا يمثل البئر العمودي. مع تقدم الحفر، يبدأ البئر بالانحراف عن هذا المسار المستقيم. مع انحراف 8° لكل 100 قدم، سوف ينحني البئر تدريجياً بعيدًا عن الخط العمودي، مما يشكل قوسًا سلسًا بنصف قطر معين.
تطبيقات آبار نصف القطر المتوسط:
تُستخدم آبار نصف القطر المتوسط بشكل شائع في العديد من سيناريوهات الحفر، بما في ذلك:
الخلاصة:
تُوفر آبار نصف القطر المتوسط، مع معدلات الانحراف المميزة لها، أداة قيمة للتنقل في بيئات تحت سطح الأرض المعقدة. من خلال تحقيق توازن بين الانحراف المُتحكم به وكفاءة الحفر، فإنها توفر حلاً عمليًا وفعالًا للوصول إلى التكوينات المستهدفة مع الحفاظ على استقرار البئر. إن فهم مفاهيم نصف القطر المتوسط وتطبيقها أمر ضروري لتحسين تخطيط وتنفيذ الآبار في مختلف سيناريوهات الحفر.
Instructions: Choose the best answer for each question.
1. What is the typical deviation rate for a medium radius well?
a) 2-4 degrees per 100 feet
Incorrect. This range is typical for low-radius wells.
b) 8-12 degrees per 100 feet
Correct. This is the standard range for medium radius wells.
c) 15-20 degrees per 100 feet
Incorrect. This range is typical for high-radius wells.
d) More than 20 degrees per 100 feet
Incorrect. This deviation rate would be considered extremely high.
2. Why are medium radius wells beneficial for targeting specific subsurface horizons?
a) They allow for rapid drilling and reach the target quickly.
Incorrect. While they are efficient, their primary benefit is controlled deviation.
b) They can navigate complex formations with minimal deviation.
Incorrect. This is more applicable to low-radius wells.
c) They maintain a controlled deviation rate to reach the target accurately.
Correct. Their moderate deviation allows for precise targeting.
d) They are the most cost-effective option for all drilling scenarios.
Incorrect. The cost-effectiveness depends on the specific drilling scenario.
3. Which of the following is NOT a reason why medium radius wells are considered efficient?
a) They require less complex drilling equipment.
Incorrect. This is a benefit of medium radius wells.
b) They can be drilled faster than high-radius wells.
Incorrect. This is a benefit of medium radius wells.
c) They often require multiple drilling stages to reach the target.
Correct. They are often more efficient than high-radius wells due to simpler equipment and faster drilling times.
d) They minimize drilling costs compared to other well types.
Incorrect. This is a benefit of medium radius wells.
4. What is the primary advantage of medium radius wells in terms of wellbore stability?
a) They create a wider wellbore, improving stability.
Incorrect. Wellbore diameter is determined by other factors.
b) They minimize sudden changes in wellbore pressure and stress.
Correct. Controlled deviation prevents sudden shifts in pressure and stress, promoting stability.
c) They allow for the use of stronger casing materials for increased stability.
Incorrect. Casing selection is influenced by other factors.
d) They are less susceptible to wellbore collapse due to their steeper angle.
Incorrect. The angle can actually increase the risk of collapse in some cases.
5. In which of the following applications are medium radius wells commonly used?
a) Shallow water drilling for oil and gas.
Incorrect. While they can be used in shallow water, they are more common for moderate depths.
b) Horizontal drilling for unconventional resources.
Incorrect. Horizontal drilling typically involves higher deviation rates.
c) Geothermal energy development.
Correct. Medium radius wells are often employed in geothermal energy extraction.
d) All of the above.
Incorrect. Medium radius wells are not typically used for horizontal drilling in unconventional resources.
Scenario:
You are planning a well to target a reservoir located 3000 feet below the surface with an inclination of 25 degrees. You decide to use a medium radius trajectory with a deviation rate of 10 degrees per 100 feet.
Task:
Instructions:
1. Total Horizontal Displacement (MD): * **Inclination angle:** 25 degrees * **Vertical depth:** 3000 feet * **Total deviation:** 10 degrees per 100 feet * 30 (100-foot intervals) = 300 degrees * **Horizontal displacement:** 3000 * tan(25) = 1400 feet (approximately) 2. Measured Depth (MD): * **Vertical depth:** 3000 feet * **Total deviation:** 300 degrees * **Measured depth:** 3000 / cos(25) = 3314 feet (approximately)
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