Water Control of Horizontal Wells Using Foam-Gel: Lessons Learnt in a Heavy Oil Reservoir with Strong Waterdrive

Abstract

As technology advances in horizontal well drilling, long horizontals completion are now preferred for producers aiming to explore more oil-bearing zones, especially in heavy or tight oil reservoirs. However, for strong waterdrive horizontal wells, abrupt increase of water-oil ratio and abounding unwanted water production severely affect the profitability of the field due to the constant decrease of oil production and premature well shutting. The targeted reservoir of this work is a typical heavy oil reservoir with strong waterdrive. By December 2014, the average water cut for the two productive layers has increased 40-70%, for some wells especially, the water cut has exceeded 95% causing frequent well shutin. Therefore, to ensure the productivity of the horizontal wells, water shutoff has become a challenging and urgent task. According to the aquifer identification and water influx diagnosis, 27 horizontal wells distributed in aforementioned two productive layers were first categorized into two groups in order of treatment difficulties, after which foam-assisted gel and gel treatments were designed and conducted. For the three of the treated wells, the average water cut was significantly reduced from 80.3% to 48.0%. Although the gross liquid production rates were slightly reduced after treatment from 31.7 to 27.7 t/d, the oil production rate was considerably increased by 28.1 t/d. By January 2016, 4 500 t of the incremental oil was produced indicating the success of the water shutoff jobs. However, it should be noticed that the water cut of the N2 foam-assisted gel treated well started to rapidly rise after two months. This is probably caused by inappropriate foam/gel volume ratio. The water control strategies and field results in this heavy reservoir will provide the necessary clues for the design and application of water shutoff treatments for horizontal wells driven by strong water.

Field Validation of a Non-logging Alternative Method for the Prediction of the Location of Water-Cresting in Horizontal Wells for Water-Drive Reservoirs

“…As lowering the production rate to lessen the effect of the pressure draw-down in order to delay water coning is often not economically viable, the use of the horizontal well with its inherently lower pressure draw-down and higher productivity compared to the vertical well becomes an attractive option. , However, the use of the horizontal well in a water-drive reservoir does not necessarily get rid of the problem of water coning entirely but merely delays it and changes the geometry of the water breakthrough from that of a point-source water coning to that of a linear water-cresting or cusping . For heavy oil reservoir, the problem of water-cresting becomes especially more severe due to the unfavorable mobility ratio . With the onset of water-cresting, the productivity of the well rapidly declines, , and in the worst case, it can lead to the well-being entirely flooded out .…”

“…With the onset of water-cresting, the productivity of the well rapidly declines, , and in the worst case, it can lead to the well-being entirely flooded out . Currently, an assortment of mechanical and chemical well interventions is available involving chemical packers, − foam gel, cross-linked polymers, dual completion, inflow control devices, − and so forth. However prior to applying any of these treatment, the location of the water-cresting needs to be pinpointed first with specialized logging tools such as the pulsed-neutron three phase holdup measurement tool or the oxygen activation logging tool …”

“…5 For heavy oil reservoir, the problem of water-cresting becomes especially more severe due to the unfavorable mobility ratio. 8 With the onset of watercresting, the productivity of the well rapidly declines, 9,10 and in the worst case, it can lead to the well-being entirely flooded out. 11 Currently, an assortment of mechanical and chemical well interventions 12 is available involving chemical packers, 13−15 foam gel, 8 cross-linked polymers, 16 dual completion, 17 inflow control devices, 18−20 and so forth.…”

Method of Predicting the Location of Water Cresting for Horizontal Wells in a Water-Drive Reservoir for Early Prevention

“…13 When water cresting occurs in a gas- or oil-producing well, it can lead to rapid production decline and/or loss of well due to rise in the water-cut. 14 − 16 To save the well, currently there are various types of mechanical and chemical well intervention methods such as chemical packers, 17 − 19 foam gel, 20 dual completion, 21 and inflow control devices. 22 − 24 But prior to their application, the location of water cresting needs to be sited first with specialized logging tools.…”

3D Physical Simulation Experiment of Edge Water Reservoir by Polymer/Surfactant Binary Flooding

“…is phenomenon, which occurs quickly, leads to a rapid increase in the water content of the reservoir. e inflow of water then limits oil recovery, leading to a significant decline in well production [1][2][3]. However, if the edge water can be effectively restrained or utilized in time, it can once again become a positive energy to improve the development efficiency [4].…”