Over time, downhole equipment and hardware can develop layers of scale that eventually prevent full functionality. Even if volumes of debris do not need to be recovered to surface, milling is still required to restore proper function to equipment such as valves.

One of Welltec’s clients encountered difficulty in manipulating an Upper Master Valve (UMV) for one of their offshore oil producers in the Niger Delta – the UMV was then confirmed to be stuck in a closed position.

A milling solution was proposed in the form of the Well Miller®, an e-line operated cleaning tool. In this case, a specially designed milling bit with a dual coupon catching mechanism was introduced to achieve surgical accuracy during milling whilst eliminating the risk of damage to other components in the well.

Prior to operations, Welltec carried out preparatory testing whereby an exact replica of the valve was successfully milled.

In the field, the specially designed milling bit safeguarded against damage to the lower master valve and ensured that the problem was not compounded by creating downhole fish. The first run was made in 33 hours with the Well Tractor® applying ~700 lbs. of weight on the bit.

A slickline investigative run was made to drift through the UMV with a 3.26” lead impression block in order to confirm that the coupons were not lost during circulation after milling.

A confirmation milling run was made which lasted for 31 hours. Subsequent pressure differential from the cement pressure line gave confirmation that access had been re-established. The 2.25” thick UMV had been successfully milled without contact to the lower master valve which was no more than 1 ft. below.

This operation ended with several noteworthy achievements.

The surgical type milling procedure represents the first ever 2.25” gate valve milling on e-line – worldwide.

Crucially, the client was able to gain full access to the well and optimize production and expressed great appreciation for Welltec’s professionalism and service delivery.

Welltec executed a clinical job over two successful runs, also retrieving both coupons after milling – avoiding cause for fishing operations.