Case History proves conducting a series of re-completions from Toe to Heel, and producing each re-completion to depletion before moving uphole to the next re-completion increases cold heavy oil recovery. Other learnings suggest further improvements.
Currently Hz wells and Vertical CHOPS wells recover about the same amount of oil. Sequenced Re-completions changes how we use Hz wells. The result is more recovery per well.
Loose uncemented sand, foamy oil, and operating at near maximum drawdown are basic requirements for economically successful cold production. At maximum drawdown, active bottom water cones rapidly reducing recovery and stranding reserves.
Hz wells were relatively new when this well was drilled. It was drilled to test a horizontal well’s recovery against two vertical wells prior to full scale pool development. In addition, the liner was segmented to test three different slot sizes for oil production and sand exclusion.
There were no loss circulation issues at this distance from the depleted vertical wells. The first 150m was in poor quality pay resulting in 700m of trajectory in effective pay. There were no problems installing or setting the ECP’s or the liner.
Pack-offs at top & bottom of the scab liner prevented crossflow from the rest of the well. The PCP was landed above the liner top near the top of the Build Section to minimize rod/tubing failure. Recovery from 245m of slotted liner was 134% of the average of off-setting vertical wells.
The scab liner was pulled to evaluate production from the entire liner. No change in production rate lead to the conclusion there was no inflow through the smaller slot sizes. An area of good pay was selected for perforating in the Mid-Section. Rate increase after perforating was 600% and similar to IP of the Toe section. Recovery was 70% of the vertical wells. The immediate up-tick in production rate plus the volume recovered indicates untapped reservoir was accessed when perforating 171m uphole from the economically depleted Toe slots.
Sand was found covering the original perfs in the Mid-Section. The sand was displaced back through the perforations to the outside of the liner. Arguably most of the incremental recovery is from the Heel. The lower IP could be caused by 55% of the Heel section in poor quality pay plus rapid re-entry of the sand in the Mid-Section. Recovery was 129% of the vertical wells. Oil price affected Economic Depletion rate. The Mid-Section reached economic depletion in 1999 when oil was <$20/bbl vs 2004 for the 3rd Sequence when it was above $40. The up-tick in rate plus the volume recovered indicate untapped reservoir was accessed by additional perforating.
This graph illustrates the up-ticks in production rate after each perforating event. Different declines could be due to reservoir quality or sand influx accumulating and throttling flow.
This table summarizes the vertical wells’ recovery and rates along with the recovery and rates from each segment of the horizontal well. Cold production horizontal wells in this area only recover about the same as a vertical well. This well recovered more than 3 times the recovery of a vertical well, and, each re-completion recovered about the same as a vertical well.
The big take-away is that a horizontal well is capable of several times more recovery than vertical wells. Currently suspended Hz wells are candidates for re-completions that would restore them to production and ultimately lead to much higher recovery. Cost Effective removal of the initial high influx of sand is necessary to maximize recovery and profitability. Since the recovery from each re-completion is similar to a vertical off-setting well’s, the number of re-completions and ultimate recovery can be estimated per horizontal well.
The technique does not require pre-installed isolation tools on the liner nor does it require plugs in the liner after the re-completion is depleted. As well, it is designed to perforate, stimulate, and put the well on pump in one run. Inflow from the perforated interval is contained such that sand & oil inflow is delivered directly into the pump intake. The pump is landed at the perforations to provide maximum drawdown maximizing sand inflow and oil recovery. Well servicing and flush-by operations can be carried out by equipment readily available locally. Besides re-completing currently non-productive horizontal wells, there are about a half dozen more opportunities for using sequenced re-completions to restore productivity and value to cold heavy oil assets.
Sequencing Re-completions in Horizontal Wells provides a step-rate improvement for lower cost cold heavy oil recovery. Contact me so we can get you ready to maximize profits and recovery when the oil price returns.