ASP (alkali-surfactant-polymer) flooding improves recovery rate dramatically. However, scaling problem happens in artificial lift systems and causes pump sticking in sucker rod pumps and the average pump running time decrease from 500 days to 37 days. By analyzing the constituents and characteristics of scales from ASP production wells and experimenting with simulating produced liquid, characteristics and mechanism of silicon containing scale forming are researched. The results show that Ca2+, Mg2+, Al3+, polyacrylamide, surfactant and silicon influence the ASP scales structures and forming processes. The ASP scales have the characteristics of absorbing and sticking. Basing on describing of scaling characteristics, mechanisms and the pump structures, the reasons for pump sticking are analyzed. Pump sticking which caused by scaling between the plunger and barrel occurs when the sucker rod pump is sucking, hot water is circulating or the pump is stopping. When the well is shut down, one major reason of pump sticking is scale particles set down, stick and pack in the anti-sand groove. When a great deal of hot water is circulating in the well bore, liquid viscosity lowers and scale particles set down speed increases also. The slow-dissolved solid scale-inhibitor SY-2 and anti-scale pump with long plunger-short barrel are developed and applied in field. Through these methods applications, the pump running time have been prolonged and good results have been achieved. Introduction ASP flooding technology improves recovery rate dramatically 1. However, alkali in ASP solution reacts with both formation fluids and mineralogical components such as kaolinite, montmorillonite and feldspar, from which silicon and aluminum components are soluted into fluids 2. With the fluids flowing and surrounding condition changing gradually, scale forming in artificial lift wells, which causes pump sticking in sucker rod pumps and the work over periods decrease. For example, without any anti-scale methods after scaling, the average work over periods are 37 days in sucker rod pump wells in a test area of Daqing oilfield, which influence the production and cause low commercial effectiveness. Silicon scale forming characteristics of ASP flooding Analysis of scale samples The typical scale samples from the field are analyzed. The well-consolidated scales are flake-shaped macroscopically and scale layers are fline vertically. The scales from oil well are not a single composition. They consist of silicon scale, carbonate scale and organic impurities. Silicon exists as silicate or SiO2, Ca2+, Mg2+ exist as carbonate. Fe exists as its oxide or sulfide or carbonate. Na and K are adsorbed on the surface of scale as soluble salts. Water is not the ingredient of the scale but it exists as absorbed water or crystal water. The characteristic functional group of HPAM such as CO-, -CH2-, -CONH2 exists in the scale, but the content of HPAM can't be quantificationally tested by Amylum-Cadmium Iodide method. Influencing factors of silicon scale formation Considering the field conditions, Na2SiO3 solution and mineralized water are made up to different simulating produced water. It is described as bellow. The temperature, correlative ion concentration, pH is changed, and the influences of these factors to scale formation are given as following. The first is silicon-only solution. The second is Si, Ca2+ and Mg2+ solution.

Strong base ASP flooding technology can improve swept volume, displacement efficiency and oil recovery greatly. It shows encouring prospects for sustainable development of the maturing oilfield. So In this paper, with the help of data from coring wells and newly-drilled wells after ASP flooding, we has strengthened understanding of the reservoir.By using numerical simulation, carrying out lab core displacement test, microscopic oil displacement test, and using techniques such as nuclear magnetic resonance, electron microscopic detection and electrical logging curves of newly-drilled wells and so on, we have found out petrophysical changes in reservoirs after ASP, evaluated oil displacement efficiency of different locations, and systematically analyzed influcing factors on occurrence of displacement efficiency differences. The study results show that the oil displacing efficiency increased by 14.7% after strong alkali ASP flooding, and the thickness of heavy-water-flooded layer increasedby 26.0%. Chemical reactions and ion exchanges between ASP fluid, rock and clay minerals lead to changes of reservoir physical properties: Shale content increased; median grain diameter decreased; Permeability of intervals lowered and the wettability is converted to hydrophilicity. petrophysical changes of the reservoir is the main factor influencing oil displacement efficiency.The research result provides a guidance to explore potentialities of ASP flooding during the commercial popularization process and it is an important reference for further studies on enhancing oil recovery techniques after ASP flooding.

ASP flooding tests in Daqing oilfield show that it can greatly enhance oil recovery and provide a powerful technical support for sustainable development of the oilfield.At present, ASP flooding in Daqing oil field has entered commercial popularization stage and the supporting technologies such as reservoir engineering, production engineering, surface engineering involved with multi-disciplinary, chemical agent quality inspection and field injection have been formed.However, there still lacks in-depth recognition about reservoir developing conditions and remaining oil distribution after alkali ASP flooding. Therefore, on the basis of analysis of dynamic and static data, application data from newly drilled wells and coring data before and after ASP flooding, this paper gives a clear understanding of the reservoir developing condition and oil displacement effect and confirms remaining oil distribution characteristics and its forming causes from macroscopic to microcosmic perspectives and from horizontal to vertical directions then to innerlayers through application of geological research,numerical simulation,lab core detection, nuclear magnetic resonance (NMR) and confocal laser scanning technology. From macroscopic perspective, there is less remaining oil scattering on the plane due to imperfect relationship between injection and production; Vertically, the top of sand body is where remaining oil richly gatheres.Alkali ASP flooding's effect is remarkable for remaining oil and heavy constituents of oil have dramaticly reduced, Especially for membranous remaining oil on the pore surface, and intergranular adsorption of remaining oil has added.

Alkali-Surfactant-Polymer (ASP) pilot and enlarged field tests are all successful in Daqing Oil Field, demonstrating ASP process can greatly enhance oil recovery by 20% OOIP and bring more economic benefits. But the previous tests were all carried in one group of wells which couldn't reflect performances and adaptability of ASP industrial application. Therefore, the commercial field test in multi-well groups with homemade surfactant has been carried out to study performances, scaling characteristics and matching adjusting technologies and to accelerate industrial generalization of ASP flood. The test shows that ASP flood is suitable for the reservoir whose connecting proportion of river channel sand is above 70%, and permeability is over 0.3um2. The larger the well space is, the longer time alkali takes to transfer in reservoir, which results in serious chromatographic separation, scaling, and decrease of injecting-producing capability. Development result can be improved by fracturing on injectors and producers, ceramsite fracturing proppant being the best choice, and by low-carbon mixed organic acid on heavily scaled producers during the late development stage to remove blockage, but the influence of scale can't be totally eliminated. Due to lateral and inter-layers’ heterogeneity in the reservoir, less recovery has been achieved than in the pilot test. We can know from the test that if the well-space is shortened in industrial application, and anti-scaling method is optimized, oil recovery will be further improved.