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rangcs i.e. 1.5D for thc uppcr laycr (1 - 2 rangc) and 0.75D for Ihe lower layer (0.5 - 1 rangę), the average penneabiliiy for the layers was calculated to be 1.33D for the upper oil sand and 0.67D for the lower oil sand. Tltis corrcsponds to a permeability thickncss of 85,800 mDft for the upper sand and 27,300 mDft for the lower sand. Assuming botli sands have bccn pcrforatcd and that one zonę has not bccn stimulatcd or damagcd differently than the other, it follows that injection would split roughly 75% into thc upper oil sand and 25% into thc lower.

One of the strengths of pressure pulsing that is claimcd is that it can improve injection conformance (vertical sweep efficiency) and areał sweep efficiency. Tltis could also be a possible cxplanation for the improved injecthity. Improved injection confonnance will result in an inerease in oil recoveiy at somc time in thc futurę. The timing of this inerease affccts thc cconomics of thc projcct, and thc sooncr thc production inerease can be achicY cd, thcbcltcr thc cconomics will be. In order to accclcratc thc production inerease it is important to inject such that thc voidagc is maintaincd in thc ltigh penneabiliiy layers as well as crcating improvcd sweep in the lower permeability layers. This will aid create a "pressure bulgc" and allow it to spread in the reservoir and help the porosiły dilation wave to propagatc further into the res ervoir.

By limiting the injection ratę to pre PPT levels an improiemcnt in injection confonnance could, in the short term. result in a temporary dccrcasc in oil production as the Yoidagc into the layers dominating production drop. With limited injection, Yvhcn thc system lias rcachcd a new equilibrium. it Yvould be expccted that thc oil cut go up. as thc less maturę zonę is likely to produce Yvith lower water cut. Again, lite timing of the oil production inerease would be linked to the Yvater injection ratę.

Not to limit water injection ratę for other than containmcnt issues is, thcrcforc, one of thc main lessons from this pilot projcct. Notę that water injection rates were also limited by the pump specifrcations at the start of the project.

2. Measurement uncertainty

The uncertainty in tlić mcasurements is such tliat no finn conclusions can be draYvn as to Yvhcthcr an oil production inerease Yvas scen or not during thc pilot project. The fluid ratę accuracy estimate is ±5%. The Yvater cut measurement accuracy is given as ±5% for water shakeout data and ±20% for Coriolis measurcmcnts due to the uncertainty in fluid density. The accuracy of these types of water cut measurcmcnts arc, however, also reliant on thc placcmcnt of the samplc point and the flow regime at that point.

3. Corrosion

The wellbore cmironment was much morę corrosiY'e than anticipatcd at thc start of thc trial and it is bclicicd tliat this had a significant irnpact towards the end of thc trial and ullimately led to the failurc of thc doYvnholc pulsc cąuipmcnt. The effect of corrosion can not be quantifled, hit for futurę projects it will be important to ensure proper materiał selection for the Yvell conditions.

CONCLUSIONS

During thc PPT field trial Iyvo of thc thrcc objcctives for thc trial were met, namcly cquipmcnt operability and incrcascd injectivity.

The equipmcnt outperformed the project scope of operating remotely for a period of five months comparcd to the target three months. The equipment achieved this even though operating in harsh Yiellbore condition in a morę corrosiic emiromnent tlian anticipatcd.

An avcragc inerease in injectivity of 30% Yvas rccordcd during thc trial with a platcau injectivity enhanccmcnt of 40% during thc first two months. The maximum injectiyity correspondcd Yvith injection pressure at 40% of the historical values. Injection pressure remained Iow even after the trial was complcted at around 70% of the steady State injection pressure for about one montli. After tliat time the injection pressure started to inerease.

It is important to notę the significance of thc injection pressure rcmaining Iow after thc PPT pilot was terminated. .

Incrcascd injection rates arc not only significant for cxisting developments. By inereasing the injection ratę per well, the Capital expenditure for neYV projects can be reduced, resulting in inereased profits and improicd economics for the project.

The injection Yvater contained 50 mg/1 hydrocaibons with viscosity of around 150 cP and 15 mg/1 fines. PPT maintaincd improicd injcctivity throughout thc stimulation period rcgardlcss of thc poor Yiatcr quality. This indicatcs that another use of the PPT technology ivould be Yvaste water disposal.

The third objectiie - to inerease oil production, is difficult to evaluate due to the absence of high qua!ity data. The most important factors arc believed to be the 1oyv paltem voidage, thc ivatcr injection ratę limitations imposed due to Yvatcr availability during the field trial and the corrosivc downholc emiromnent. With thc assumptions outlincd in the paper. it would take around 18 years to inject one hydrocarbon pore Y olume of Yiatcr in this pattern. Even accounting for non-idcal factors it would be very difficult to get rcsults in five months if thc porosity dilation waves could not be madę to propagatc from the injector to the producer. Oicrall, with the limitations imposed. thc projcct is viewed as a tcchnical success.

RECOMMENDATIONS

For futurę projects it is recommcndcd that: