Symmetrix Overburden Drilling System & Reverse Circulation Drilling System

Objective

To drill boreholes by symmetrix method or reverse circulation method

Drilling Technique & Equipment

Prior to this method of drilling being utilised the site will have been prepared and a thorough safety check been carried out.

The rig will be reversed over the drill target site using every care to get as near to the proposed drill target as possible. When a secure base for the rig has been achieved the mast will be erected and final levelling will take place.

Rotex OY Symmetrix drilling method using symmetrix nominal 300mm system or equivalent system.

This drilling method comprises full face drilling with reamer shoe, slightly oversized, attached to nominal 300mm threaded steel casing. Following uPVC & gravel pack installation, where specified, retrieval of steel threaded conductor symmetrix casing is assisted by the oversized hole to the outer casing and in addition our Drill Rig has a floating bottom clamp to assist the rotary head with pull back offering a combined pull back of 50-60 ton.

We can offer a Symmetrix system with an ID of 273mm, allowing installation up 250mm screen/casing string without gravel pack or grout seal or 200mm with gravel pack and grout seal.

Reverse Circulation Drilling: The use of dual wall drill pipe combined with drill collars/stabilisers and special hard formation bits mean a cleaner drill site and drill system that is environmentally 'greener'. Drilling cuttings are directed into holding tanks or pits and all surplus clean drill fluid is re-directed down hole as part of the drilling operation. This method allows borehole advancement by" mudding" up unstable openhole with appropriate mud mix/polymer to drill to target depth and install uPVC string prior to removing mud out of hole by appropriate well development techniques.

Rig Specification

- Rig No. 1; Knebel Rig 97 TBR and

- Rig No. 2; Knebel Rig HY76-BRS.

Well Head Finish

The casing to be finished above ground level with full specification well head finish per tender outline.

Borehole logging & Sampling

A detailed borehole log is to be provided. Samples of sediment encountered at 1m intervals are to be left in a chronological order on site near the borehole.

Down Hole Hammer Drilling

Objective

To drill a test or production bore hole in a safe and efficient manner and respecting the surrounding environment.

Rig Setup

Prior to this method of drilling being utilised the site will have been prepared and a thorough safety check and risk assessment carried out. The rig will be mobilised to the drill target site. Final plumbing and centralising will be completed utilising hydraulic jacks and packing plates to ensure a secure base for the rig. When this has been achieved only then the mast will be erected and the final levelling will take place.

Drill String

Drilling is attained by the use of a rotating drill head with the drill rods screwed into head. The drill string is that part of the drilling unit which works mainly within the borehole, connecting the surface drill Rig to the drill hammer & bit at the bottom of the drill string. In effect the main function of the drill string is the efficient transmission of power in the deepening hole. As required the drill pipes are mechanically lifted into place over the previous drilled pipe which is standing generally 1 mtr above surface and clamped in the drill table. The next pipe is then screwed into the last drill and torqued up. The Rig is ready to commence/continue drilling.

Down Hole Hammer Technique

Down hole hammer is the process by mechanical & hydraulic motion which the "top drive head" is attached to the top end of drill string and through a combined process of an air operated piston within the hammer striking(percussion) the button bit attached to the bottom of the hammer, in addition to air and water and foam additive necessary to flush out the hole as drilling proceeds.

Discharge water and drill cuttings

Discharge water and drill cuttings will disperse around the protruding steel liner where the well is under construction at the back of the Rig. The water will run away with the fall of the site. Where appropriate procedures can be put in place to contain the water and dispose of it through surface pumping and or treatment across lay flat piping to an appropriate discharge point.