Learnt from Formation Damage Problems to Design Selection of Produced Water Treatment for First Full Field Development Steam EOR Oman
- Ardian Nengkoda (Petroleum Development Oman) | Mohd Habsi (Petroleum Development Oman) | Ahmed Salmi (Petroleum Development Oman) | Ilangovan Annamalai (Petroleum Development Oman) | Dilshad Ahmed (Petroleum Development Oman) | Sameer Sariry (Petroleum Development Oman) | Hamoud Hadhrami (Sultan Qaboos University)
- Document ID
- Society of Petroleum Engineers
- SPE EUROPEC/EAGE Annual Conference and Exhibition, 14-17 June, Barcelona, Spain
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
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The X field of Oman is a highly fractured carbonate field. The main oil bearing reservoir is the Shuaiba/Kharaib formation. Full development of the field will result in large water production that will have to be disposed off. Plan is to inject the produced water into the Al Khlata sands. The availability of sufficient water disposal capacity is a crucial element of the X steam project. If this capacity is constrained, water production from the X field is limited and it may not be possible to maintain the oil rim at the completion depth of the fracture rim producers. This may cause the oil production of the whole field to be deferred. For the base case, the total forecasted water production ranges from 63,000 to 74,000 m3 /d for 30 years. During pilot plant operation in year 1998-2000 and cold production, the formation damage and loss injectivity have been reported at produced water disposal wells. The main objective of this study is to ascertain the cause of rapid injectivity loss and input design for facilities selection. The assessment are cover the oil and solid particle size, fluid chemistry and compatibility, suspended solid in disposed water, the impact of oil in disposed water, fine migration (critical velocity test) and proper produced water treating facilities selection (equipment and technology).
The X Field is located in central Oman south of the western Hajar Mountains. This large oil accumulation is trapped in shallow Cretaceous limestone units at a depth of around 200-400m subsea. The anti-clinal structure is a result of a deep salt diaper, with significant crestal faulting and fracturing. The field was discovered in around 1970 and contained 16° API oil with a viscosity of 220cP has been produced from the 29% porosity, low permeability (5-14mD) limestone. During the primary production the first year showed a large peak in oil mainly from emptying of the fracture network with a minor contribution from fluid expansion due to pressure reduction. At the end of the first year, production had declined to a very low sustainable rate interpreted to be from gravity drainage, from a combination of gas-oil (GOGD) from the secondary gas cap and oil-water (OWGD) below the fracture gas-oil contact (FGOC). The reservoir then consists of a matrix with very little drainage and a fracture network with a thin oil rim below the secondary gas cap and above the fracture oil-water contact (FOWC), Figure 1.
Primary production performance such as that of X Field is only expected to recover some 3-5% of the oil in place over any reasonable time frame due to low matrix permeability and high oil viscosity on gravity drainage rates. Recoveries via steam were discounted as development options due to the pervasive fracturing observed in the field which would encourage the flooding agents to completely bypass the matrix. Full development of the field will result in large water production that will have to be disposed off. Plan is to inject the produced water into the Al Khlata sands. The availability of sufficient water disposal capacity is a crucial element of the X field steam project. If this capacity is constrained, water production from the X field is limited and it may not be possible to maintain the oil rim at the completion depth of the fracture rim producers. This may cause the oil production of the whole field to be deferred. For the base case, the total forecasted water production ranges from 63,000 to 74,000 m3/d for 30 years.
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