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Kikeh Field is a deepwater project located in Malaysia. The development plan for this field requires fifteen water injectors, eighteen producers, and one gas injector to be completed in more than 4,300 ft of water depth. In order to maintain the oil production target for this field, the water injection rate should double the target oil rate. To achieve this, water must be injected into the formation at fracturing pressures. The completion campaign started with three water injector wells. The initial results were not as expected, i.e. after pumping 1000 bbls of treated seawater at rates from 7 to 14.5 bpm, surface pressures were still within the pressure limit of 3000 psi, given by the Floating Production Storage and Offloading (FPSO) facilities. However, the injection rate was decreased with increase in pressure, and skin factor was found to be increased. Another observation was that the formation was not fractured at pressures exceeding the expected closure stress. Possible explanations for such behaviour were: (1) the development of a "temperature" sensitive emulsion in the reservoir matrix, (2) the effect of temperature in viscosity of our seawater crude, (3) near wellbore damage caused by fines from the injected water blocking the near wellbore region. When a second injectivity test on the second well was conducted, again the injected rate was not able to create fracture even though the injected pressure was above the breakdown pressure. After analyzing the injectivity data, another mechanism related to poroelastic stress was postulated. Poroelastic stress is a transient localized stress increase caused by fluid injection into porous media. Possible explanations have been looked in details using pressure transient data and it supports the theory of poroelastic effect. Then the remedial action was selected to overcome poroelastic behaviour in the Kikeh field. The operation procedure and the result obtained after injecting Viscoelastic fluids at fracturing rates are discussed in this paper. This paper also describes the evaluation of skin after each injectivity test from pressure transient analysis. |
