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Effects of Reservoir Boundary Conditions, Drainage Shape, and Well Location on Productivity of a Vertical Well
Lu J., Yang E., Rahman M.M., Wang X.
This paper gives a review of steady state and pseudosteady state productivity equations for an unfractured fully penetrating vertical well in a permeability anisotropic reservoir. This paper also studies the effects of drainage area, reservoir boundary conditions, drainage shape, and well location on productivity. The production performances of an unfractured vertical well in a circular reservoir, a sector fault reservoir and a rectangular reservoir are studied and compared. Mechanical skin factor is included in the productivity equations. This paper examines the steady state and pseudosteady state production performance of oil wells with constant flow rates in different drainage shapes, a library of productivity equations is introduced, several combinations of closed and/or constant pressure boundary conditions are considered at lateral reservoir boundaries. The equations introduced in this paper can be used to determine the economical feasibility of a drilling an unfractured fully penetrating vertical well. It is concluded that, drainage area and reservoir boundary conditions have significant effects on productivity of a well, and productivity is a weak function of drainage shape and well location.
Efficiency of the Green Surfactant Derived from Avena sativa Plant in the Presence of Different Salts for EOR Purposes
Azdarpour A., Norouzpour M., Nabipour M., Santos R.M., Mohammadian E.
In this investigation, a unique approach using a green surfactant extracted from the Avena sativa (AS) plant in conjunction with three different salts, including Na2CO3, NaCl, and Na2SO4, was examined for enhanced oil recovery. In addition, the efficiency of NaOH as a supplementary chemical in the process was investigated. Based on the results of the interfacial tension (IFT), the optimum value of NaOH was found to be 2,000 ppm, while the green surfactant had a CMC value of 4,000 ppm. The IFT value at the CMC point of NaOH was 2.34 mN/m, when the FB was used, and the IFT value was 2.78 mN/m, when deionized water was used. In addition, in terms of IFT reduction, wettability modification, and oil recovery factor enhancement, Na2CO3 was the most suitable salt with the AS surfactant at the CMC point (4,000 ppm), followed by NaCl and then Na2SO4. The IFT values at the optimum salinity point (10,000 ppm) of Na2SO4, NaCl, and Na2CO3 were 3.18, 3.05, and 2.87 mN/m, respectively. Moreover, the contact angles at the optimum salinity point of 10,000 ppm after 150 hr and at the reservoir temperature (80°C) were 36.58°, 40.76°, and 44.18° with Na2CO3, NaCl, and Na2SO4, respectively. Furthermore, the addition of NaOH improved the efficiency of the green surfactant in terms of maximizing the recovery factor by decreasing the IFT values and changing the wettability of the rock toward a more water-wet state. The final recovery factors of 88.45%, 80.87%, and 7.98% were attained using Na2CO3, NaCl, and Na2SO4, respectively, when 1 PV of NaOH was injected as the preflush, followed by 4 PVs of natural AS surfactant.
