# Reservoir and Geological factors affecting Radial Drilling performance



## alwardrus (14 مارس 2008)

Radial Drilling Technology is an hydraulic jetting method to penetrate the reservoir/formation perpendicularly from the existing cased or non-cased well bore. This is achieved by opening a hole of about 2.5cm in the casing using a combination of coil tubing, PDM type motors, flexible drive shaft and milling bit. The actual formation penetration is achieve by a combination of coil tubing, Kevlar type high pressure flex hose and a combination jet. High pressure is applied to the jet which has forward and reverse jet openings to

a) Penetrate the formation by hydraulic impact and erosional forces, and
b) Pull the system into the jetted hole by hydraulic reverse jetting force to attain distance and horizontalness.

To penetrate with angular hydraulic forces the jetting mechanism needs an erosionable formation (porosity) and a diameter restriction for the reverse jets to be effective inside a bore hole filled with fluid. Hydraulic forces have a limited force extension in fluid filled media.
Factors that will affect penetration of the Radial Drilling Technology into the formation/reservoir are:

· Dipping formation: The forward jet will cut into the cap rock, and depending on its hardness and/or porosity difference from the reservoir rock, the forward movement will be reduced or halted as a function of the reduced jettability of the formation.
· Unconformities/Pinch-outs: Facial changed and composition of the formation that are different from the physical composition of the reservoir rock will result in the stalling or stoppage of the jetting movement.
· Mineralization: Calcite or siliceous mineralization in carbonates or sands can result I zero porosity and will not allow the erosional effect of the forward jets to penetrate.

· Amorphous rocks: Chert’s, flints, boulders and brecciated glacial remnants or quartzitic boulders in Conglomerates will stop the penetration of the jet as a result of zero porosity that these fragments display in the formation.

· Cavernous rocks: Chemically leached into carbonates or water erosion in the sand reservoirs can produce caverns of sizeable dimension. The forward penetration of the jetting system needs a certain diameter to be effective. Once the diameter exceeds the hydraulic effectiveness the forward movement will be stopped.

· Unconsolidated Formations: Beach sands and highly erosional un-cemented sand deposits may “wash-out” as a result of the high velocity impact of the reverse jets and a a result create a cavernous spot in the formation leading to possible slow down or complete stoppage of the forward movement.

· Low-to no Porosity: Cristaline rocks, Anhydrites, Gypsum and some other evaporates nay have basically no porosity hence no jet erosional surfaces and penetration may not be possible.
· Salts: NaCl deposits occur frequently in sedimentary basins. These rocks are amorphous and not penetratable with basic jet forces. Some penetration may occur as a result of the fresh water impact on the salt formation.

Note: The forward movement (pull) of the jet system is made possible by exerting a very high velocity jet power to the formation a specific angle. This force is exerted in a fluid filled hole and as such has only limited power over distance. Additionally the “pull” has to overcome the friction of the flex hose behind the jet as is enters into the jetted hole.
As the hole washes out, these hydraulic pulling forces decrease to a point where the hole size is such that the forward power decreases its effectiveness inversely proportionally to the size of the resulting hole. In very low porosity and hard formations the jetting force creates a much smaller hole and the friction caused by the trailing flex hose will eventually exceed the forward pulling power and the system will come to a halt.
The above is the reason why pre-well selection and detailed information of the candidate wells is important for maximum result chances.


كم جزيل الشكر و خالص التحيه
أستاذ دكتور - أنور الورد
ماجستير استثمار حقول نفط و غاز. جامعة أوفا الحكوميه التقنيه للنفط روسيا الاتحاديه1997 . 
دكتوراه تصميم و تعميم مشاريع أنتاج النفط خلال عمليات الاغراق. جامعة أوفا الحكوميه التقنيه للنفط روسيا الاتحاديه 2003
في الوقت الحاضر - مدير عام لمجموعه تصميم و تحليل مشاريع الانتاج للقطاعات النفطيه غرب سيبيرياء. شركة باشنفت باشجيو بروجيكت

في الوقت الحاضر - أستاذ دكتور بجامعة أوفا الحكوميه التقنيه للنفط كليه المعادن –جيلوجيا –حفر – استخراج – استثمار. حيث أقوم باعداد اخصائون في فيزيا وهيدروديناميكا المكامن النفطيه 
تحياتي لجميع المهندسين
بريدي الالكتروني

[email protected] 
الشركه
http://www.geo-project.ru/eng/


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