SLICKLINE

While doing hole scrapping job with Gauge cutter encountered hard heldup at tubing hanger. After jarring released heldup and found a rubber seal inside GC. 

This is a common encouter in post HF well as the same situation was faced either knowingly or unknowingly.

Root cause:

Tree Saver is an equipment used during HF operation to seal and isolate X-mas tree from high pumping pressures. A hollow stem with sealing shoe extends inside X-mas tree and seals below tubing hanger.

But while removing the stem after HF job the seal often gets stuck inside tubing hanger.

While a responsible job contractor let's the operator aware of the situation, many a times it is left unknown.

During flow backs the rubber particles often block the choke bean causing problems in flow back operations.

It also cause severe problems in well intervention operations like Slickline as face in present case study.

The Seal can be fished by using proper size GC with sharp edge or an external grab.

One of flow assurance problem often occurs in Oil wells is the paraffin deposition inside tubing. Over the time deposits can completely choke tubing resulting in production loss. 

In ONGC, Rajahmundry Asset the Malleswaram oil field is a prolific and having almost Nil water production. The zones present at a depth of 3500mts appx and HF operations greatly increased production. Along with production the paraffin deposition also increased drastically.

Measures like Hot oil circulation, Chemical injection and Hole scrapping are being implemented to deal with paraffins

One of cost effective solution has been Hole scrapping with slickline. When wells are scheduled properly for hole scrapping , paraffins are effectively removed from tubing and helps maintain production. The Slickline operation can be done with in a day time with minimum equipment and manpower unlike hot oil circulation with CTU.

As seen in images the paraffins can be very hard to remove and needed heavy jarring operation with heavy weight tools to clear the obstructions. Some wells can produce paraffins at very quick pace and requires scrapping with in a month time. Wax cleaning jobs needed careful study and planning of job to avoid risks of blowing of tools which can cause fishing and equipment damage.

When well is left for a long period with out any mitigating measures the paraffins gets hard and dry which needed costly CTU hot oil circulation.

The paraffins are only seen upto 400-500mts from surface in Malleswaram. Below this depths the sub surface temperatures help inhibit paraffin formation.

Proper study and data gathering of such flow assurance problem can help deloy cost effective mitigating measures.