Research On Steam Flooding Technologies For Development Heavy Oil In Medium Depth Reservoir Of Qi40 Block And Its Application

Qi40 block located in LiaoHe oilfield began to steam soaking in 1987. With the degree of steam soaking increasing, the pressure in reservoir and the annual yield of old wells have decreased, the development effect and economic benefit becoming bad .To improve crude oil recovery and increase economic recoverable reserves, we have to convert to steam flooding. In general other domestic and international oil field view the steam flooding as the continuation of steam stimulation technology, but the depth of Qi40 reservoir is more than 1000 m. Steam flooding applied to such a reservoir is the first test at home and abroad, without the experience of mature can be referenced. Therefore, in view of reservoir characteristics and pre-throughput development and production of steam flooding in Qi 40 block. This article used theoretical analysis, lab experiments, field test and application of numerical simulation and other methods, and studied on steam flooding theory applied to the mid-deepth heavy oil reservoir and its field applicable technology.The reservoir geological features, situation of pre-development and the distribution of the remaining oil have been studied systematic.The results showed that, propriety of barrier between LianⅠlayer and LianⅡl ayer is good, the porosity and permeability characteristics in the reservoir can meet the requirements of steam flooding. Go through development of steam soaking, the whole horizontal plane has been swept but not even. Vertical heterogeneity of oil reservoir, steam overlay in oil layers and other factors caused sweeping not even in vertical direction The result of data statistics show that, herefore, the potential of continuing steam soaking in Qi40 block is limited, and there is no room for adjusting wells and vertical reservoirs to enhance oil recovery, converting to steam flooding is an useful mean of improving oil recovery. And we forecasting that converting to steam flooding can enhance oil recovery more than 20%.In view of reservoir geological characteristic, through the core displacement experiment,we carried out research on mechanism of enhancing oil recovery by steam flooding. The micro-displacement mechanism have been refined, having obtained the result of the value of the contribution caused by a variety of displacement efficiency. The function of conventional water drive is one of most important oil displacement mechanism in process of steam flooding and it contribute to oil displacement efficiency is 41.60%~46.42%; The function of viscosity reduction and thermal expansion is one of most important oil displacement mechanism in process of thermal water zone. The function of viscosity reduction and thermal expansion of 200℃thermal water flooding contribute to oil displacement efficiency is more than 15%;Effect of steam distillation of crude oil in porous medium is complex mechanism of improving oil displacement efficiency, which is influenced by reservoir pore structure, oil saturation, temperature of steam, formation pressure, steam injection rate; The influence to relative permeability also is important mechanism of improving heavy oil recovery.Base on geological factors of Qi40 block, we demonstrated that it is feasible to carried out steam flooding test, studying on the influence of the oil layers thickness, viscosity of crude oil, oil saturation, reservoir heterogeneity, the net thickness ratio of reservoir, the depth of oil layers to development effect. On this basis, we put forward the screening standards of the reservoir for the steam flooding . The study show operating conditions of steam flooding :we demonstrated that inversed 9 point pattern whose well distance is 70m is feasible to be applied to steam flooding; numerical simulation abtained steam flooding optimal parameters for the injection-production in Qi 40 block: Steam injection rate≥1.6t/ d·ha·m; injection production-injection ratio>1.0; dryness fraction in bottom hole>0.4. We put forward optimal design , methods and the implementation of specific steps of the steam flooding, and we got the capacity of injection and production of single well flooded by steam, well pattern and spacing ,perforation model to optimize and Optimization.Four well groups of steam flooding have been chosen in pilot test area, nine well groups of steam flooding in enlarged scale area and nine wells in peripheral as simulation area, carrying out planer mesh and division of vertical simulation layers, so that we set up geological model for tracking Simulation for steam flooding in Qi 40 block. We do history matching on reservoir model which have beren set up. Given the biggest periodic output and the smallest BHP, matching the liquid yield, the oil yield and the average reservoir pressure index, and the result show that the simulation calculation of development performance are fit well for the actual performance. Providing a basic for tracking simulation and dynamic forecast for steam flooding. On the basis of better fitting of the steam injection parameters, output, pressure, temperature, getting the new understanding of the reservoir by the numerical simulation. We proposed new effective adjustment measures for steam driving in the reservoir management, steam injection and oil production.Based on these preliminary research results, carrying on in the mid-depth reservoir for the first time in world .We carried out the pilot test and enlarged scale test of steam flooding: the cumulant of injection steam is 140.81×10~4t, cumulant of liquid output is 111.12×10~4t, the production injection ratio is 0.89 at present stage, the oil gas ratio is 0.18 at present stage, the recovery percent is 28.68% at present stage in pilot test area; the cumulant of injection steam is 111.12×10~4t, e cumulant of liquid output is 75.53×10~4t, the production injection ratio is 0.68 at present stage, the oil gas ratio is 0.10 at present stage, the recovery percent is 8.39% at present stage in enlarged scale test area. The results of test show that: the test area go through formation, enlargement, breakthrough of steam zone, which is fit for mechanism of steam flooding applied to oilfield development, and production performance of well groups present the typical production characteristics of steam flooding. The volumetric sweep efficiency of well groups driven by steam reach 52%, which shows that pilot test compared with index of success steam flooding in world is very successful. This proves that the steam drive technology, optimize design and adjustment measures have advanced and practical value proposed by this paper. At present stage, the oil gas ratio is 0.10 but that in designed program is 0.23. And with yeas of production increasing, the effect of steam flooding will be improved obviously. We made the economic evaluation for the pilot test and enlarged scale test The results of economic evaluation show that, the average unit operational cost of well groups in pilot test is 562.62 Yuan/t, four pilot test wells group input-output ratio is 1:1.44.And that in enlarged scale test is 958.89 Yuan/t, nine wells group input-output ratio is 1:1.39. Contrasting with indicators of success steam flooding in world, Steam Flooding in Qi 40 block is very difficult. Its technical level and test results are forefront of steam flooding field in the world. As mention to production of heavy oil, this is successful and the light of the examples of steam flooding exploitation...