Technical Feasibility Of Steam Flooding In Serious Water-flooded Heavy Oil Reservoir

The steam stimulation of Jin-45Block where the geo-pressure is only2.91MPa for nowhas been wandering into anaphase. In the serious flooded area，the average daily oilproduction of single well is only1.0t/d, water cut is92.8％, recovery rate of water is up to200%, and the oil recovery rate is0.51%. The produced percentage of recoverable reserve is92.6%. The remaining oil in this water-flooded area can hardly be exploited by thedevelopment method of steam stimulation, which makes the transformation of this methodmore and more urgent. It is quite a risk to spread the development method of steamstimulation for the edge and bottom water reservoir. To conform the water-flooded layersteam flooding feasible needs to learn the invasion feature of the reservoir edge water, tohandle the controlling elements of the edge water invasion, also to avoid the risk of steamflooding development efficiently.In this paper, the numerical simulation of steam flooding in heavy water-flooded area hasbeen carried out first, and then comes the visual physical model research of the controllingelements of water invasion. Also we focus on the analysis of the steam flooding feasibility inwater-flooded area by combining the mathematical and physical models.Using Petrel we define a fine geological model for these two test well groups, then withCMG we carry a steam flooding forecast for5years on the basis of steam stimulation historyfitting during the period from Jan1st,1985to Sep1st,2011, and also the injection-productionparameters optimization. A huge body of edge and bottom water has been set around themodel during the simulation process. Numerical simulation results show that the invasion lawis given priority to with bottom water coning, while the edge water is not widespread, and thewater-flooded situation formed by outer channeling is serious. In addition to the Yu I35layerand Yu I36layer, Oil reservoirs have basically formed heat source. The remaining oilsaturation is still45%, and the geo-pressure is2.91MPa. The increasement of geo-pressurecaused by the continuously steam injection for the steam flooding wells may restrain thewater invasion speed. With5years’ steam flooding in the serious water-flooded area, therecovery degree can be improved, and the cumulative recovery degree reaches7.74%.Carrying out physical model experiments needs the invasion controlling elements tocorrect the characteristic interpretation of reservoir water invasion. We focus on the sensitivityanalysis of the invasion controlling elements, also come up with the security technology ofedge/bottom water controlling. The heterogeneity, temperature, pressure of geosphere, and thesensitivity of edge/bottom water invasion to the edge water distance are analyzed throughexperiments. For the homogeneous core model, the temperature is set to45℃, andrespectively differential pressures are set as0.035MPa,0.045MPa and0.045MPa. For theheterogeneous core model, of which the temperature is45℃, respectively differential pressures are0.04MPa,0.06MPa and0.06MPa. When it comes to the homogeneous modelwith a differential pressure of0.055MPa, the temperature are set to45℃,60℃,75℃respectively. The fluid, the oil and water produced quantities of each well are measuredseparately through the water flooding experiment with fully saturated core model, also thefunctional equations of instantaneous water invasion, differential pressure and temperaturesare taken shape.Visual experimental researches for water invasion are all taken under the conditions ofsaturated oil and80℃of experimental temperature. When using the homogeneous coremodel, the differential pressure is set as0.10MPa,0.12MPa and0.14MPa respectively. Forthe heterogeneous core model, they share the same differential pressures. Water invasionpictures during different periods are collected through the image acquisition system. With theanalysis of edge-water invasion laws, the functional equations of instantaneous water invasion,cumulative water invasion and time for these differential pressures are built.With laboratory experiments we analysis the produced fluid of each well in the pattern.We find the well closer to the edge-water gets bigger influence, while the fluid productions oftwo wells equidistant from the edge-water are quite different, the laws of which are alsodistinctly different under various differential pressures. That may explain the edge-waterinvasions are not evenly but have their very own encroachment channels, and the laws offormation and expansion are not the same. Under various differential pressures instantaneouswater invasions all shows linear increasement. Fitting instantaneous water invasions anddifferential pressures we can get exponential functions. Edge-water immerses along the highpermeability layer to the bottoms of production wells, and then under the differential pressuregets coning to production wells. The different fluid productions of two wells equidistant fromthe edge-water also show us the invasions are not evenly. Through comprehensive analysis wefind with the bigger differential pressure, the sooner water breakthrough in production wells.Instantaneous water influx shows linear relation with time, for the higher the temperature, thelater water breakthrough. Through the water-invasion visual experimental research, we realizethat after the edge-water immerses into the reservoir pore system under the action ofdifferential pressure, firstly it mixes with bound water, and then due to the great oil/waterviscosity difference of heavy oil it flows through mini-pores dominated by bound water, theninto small pores, and then into larger pores. On the other hand, it wedges along the walls oflarge pores saturated with oil, then with the water increase the front of edge-water movingahead gradually, the invasion would go further and further till the water breakthrough, andthen the water continues to increase until a stable state. Water invasion law is divided intothree phases: water connection, water invasion and stable water invasion.In conclusion, transforming the steam stimulation of serious water-flooded reservoir intosteam flooding, and improving the injection-production relation on blocks can get the layersenergy timely replenished, get the edge-water invasion suspended, get water cut increasingrate controlled, and get the block development effect improved. Transforming in central anddraining from the edge will effectively control water invasion. Through the overall analysis of the water-invasion laws we can get the water-invasion directions and the flooded degrees toavoid the risk of steam flooding development efficiently. The idea that serious water-floodedwells as the key implementation objects and peripheral water wells as auxiliaryimplementation objects, is helping to achieve "Line A for draining, Line B for producing".Therefore, transforming Jin-45Block serious water-flooded reservoirs of Liaohe oilfield tosteam flooding development is feasible.