Oriented Perforating as a Sand Prevention Measure. Case Studies from a Decade of Field Experience Validating the Method Offshore Norway
- Jamie Stuart Andrews (StatoilHydro ASA) | Havard Joranson (StatoilHydro ASA) | Arne Marius Raaen (Statoil ASA)
- Document ID
- Offshore Technology Conference
- Offshore Technology Conference, 5-8 May, Houston, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2008. Offshore Technology Conference
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- 583 since 2007
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Oriented perforation is a technique that has been used by Statoil on manyfields on the Norwegian Continental Shelf (NCS) during the last decade. Bytargeting perforations in the most stable direction with respect to the in-situstress field, one achieves perforation tunnels with optimal "structural"strength for the inherent material strength of the formation rock. For highangle wells in normal faulting environments, this equates to shooting in (ornear) the vertical plane through the well path.
Prior to 2000 the tool design for passive orientation was generallyinadequate and misalignment of perforations was a distinct possibility.However, collaboration between operators and service companies has lead tosignificant improvements in orientation systems during the last years. Severalsuppliers now offer orientated TCP systems that are qualified for use inStatoilHydro. Some of these include devices for accurately measuringorientation during perforating.
The operator has chosen oriented perforating as a sand prevention measure inmany NCS assets including platform and subsea developments, mature fields andHPHT reservoirs. In many cases the operator believes that oriented perforatingis a preferred alternative to mechanical sand control measures. This isdiscussed in the paper together with the operators operational and productionexperiences from these applications.
Several years experience confirms that good orientation accuracy can beachieved and designed for. Oriented TCP service has shown a good track recordeven in well sections with relatively high dogleg or low orientation. Despitethe fact that oriented perforating is primarily applied in wells withdeviations over 60o, the operator has some sub 50o applications where goodorientation was also confirmed. A large body of production experience fromseveral fields confirms that oriented perforating can be a good sand preventionmeasure in suitable fields. Experience in fields with over 350 bar depletion ispresented. The operator suggests that the field data is an excellentconfirmation of its sand prediction models and, more generally, of the in-situstress conditions prevalent on the NCS. Furthermore, it is considered that thesuccess of oriented perforations is an indication of a normal faulting patternon the NCS. This is in contrast to what has been published by other parties onthe NCS.
Despite a very good success rate with mechanical sand control, a guidingstrategy in Statoil has been to avoid mechanical sand control wheneverpossible. This is due in part to cost and logistical issues but also to theplugging and productivity decline potential inherent in sand controlcompletions. This is especially true in poorly sorted formations withsignificant fine fractions and for formations where downhole scale may formupon water breakthrough (ref 1-10).
Oriented perforation is a technique that has been used by the operator onmany fields on the NCS during the last decade. By targeting perforations in themost stable direction with respect to the in-situ stress field, one achievesperforation tunnels with optimal "structural" strength for the inherentmaterial strength of the formation rock. For high angle wells in normalfaulting environments, this equates to shooting in (or near) the vertical planethrough the well path.
Several orientation systems exist in the industry. For TCP applications theorientation is achieved by passive, gravity based systems. Significantimprovements in designs have occurred over the last 6-8 years in order toimprove orientation accuracy (ref 11-14).
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