Advanced Materials Research Vols. 524-527

Abstract: Strong base ASP flooding technology can improve oil recovery by 20%, but the lifting system exists serious scaling problems which cause pump detection period shorter. The main composition of the scale are organisms (heavy oil is in majority), carbonates and silicates. The content of each component is closely related to pH value. With high pH value, the main composition of the scale is silicate. With low pH value, the main composition of the scale is carbonate. The results of analysis of the relationship between scale composition, scaling position and depositional sequence showed that the content of silicate gradually increased from top to down in shaft while the carbonate decreased. In the process of scale deposition, carbonate scale emerged at first and then it provided attachment points and crystal nucleus for the silicate. The rough surface of carbonate scale increased the friction between the fluid and the wall, it promoted the formation of silicate. Statistically analyze the properties of pH value, alkalinity, calcium, magnesium, silicon, polymer, viscosity, surfactant, fluid yield, water content in produced liquid and their influences on scaling in the injection-production period. Establish the prediction basis using the pH value as primary and ion content as supplement for the problems of mechanical production well scaling. In the period of carbonate scaling (pH10.5), the process slowed down. The coincidence rate was 93.9% after pilot tests. It provided a basis for taking corresponding measures to inhibit scale formation.

Abstract: In order to decrease the purchasing cost of pumping units and select the proper type of pumping units, the synthetic evaluation for pumping units based on fuzzy theory is studied. Firstly, the primary evaluation index and secondary evaluation index are built according to the oil and gas industry standard, and absolute comparison and relative comparison are also introduced. Then, the fuzzy weight factors of each evaluation index are determined and the fuzzy matrix operation for pumping units is made. Finally, the evaluation example for three pumping units is done to verify the correction and rationality of the method in this paper.

Abstract: Oilfield produced water geothermal resource that is very easy overlooked or wasted in the exploitation of oilfield geothermal resources is a special form of sedimentary basin geothermal resource. Based on detailed analysis of oilfield produced water geothermal resource formation mechanism, its concept is firstly proposed. The paper expounds oilfield produces water geothermal resource characteristics from three aspects of resource potential, development cost and market prospect, proposes the idea of using heat and adverse water, discusses the feasibility of development water geothermal resource to service in oil production and circumjacent dweller by using heat pump technology and lays a solid foundation for its in-depth exploitation.

Abstract: Oil spill; Source identification; δ15N; Nitrogen isotope profile; biodegradation Abstract. A preliminary evaluation of nitrogen isotope analysis as a novel, alternative method for identifying spilled oils is presented. The nitrogen isotopic compositions of crude oil from different oilfields in China may be significantly different, which provides a way of screening possible sources for spilled oil of unknown origin, especially in areas of heavy tanker traffic carrying oils from different geographical regions. The value of δ15N increases gradually with the degree of biodegradation. This findings can be applied for correlation and differentiation of spilled oils at their lightly to moderately weathered stages.

Abstract: In this paper, the FDM-Program FLAC3D is used for the 3D simulation of fracture propagation on a field scale model, based on field data of a Rotliegend tight gas reservoir in North Germany. This reservoir was treated hydraulically by a massive fracturing. The results regarding the fracture propagation were compared with those in the semi-analytical P3D simulator FracPro. It was noticed that the original code FLAC3D was unsuitable for the applications of hydraulic fracture. In further investigations, our own developed algorithm with a moving boundary condition based on discontinuum mechanics was implemented in FLAC3D. The results showed a relatively good agreement with those of FracPro. The advantage of the new algorithm is above all that irregular fracture front can be realistically simulated, which in turn reflects the stress states in multi-layers and their different rock mechanical properties

Abstract: Cluster analysis is a multivariate statistical method of the study of sample (or variables) classification, gradually classified by the analysis of the sample or the similarity between the variables. In this paper, taking the case of Daqing low permeability reservoir, according to the movable fluid saturation, the average throat radius and the starting pressure gradient, we used cluster analysis method to conduct the multi-parameter classification of low permeability porous media, and achieved good results. The results showed that: The method in low permeability porous media category is feasible and has strong rationality.

Abstract: In this paper, the indexes have been determined for identifying ineffective injection production circulation and corresponding mathematical model was constructed with fuzzy theory. Application examples show that this method is simple, fast and accurate. For high and superhigh water cut oilfields, because of the long-term erosion of injected water, there are some high penetrative channels between the injection and production wells, resulting in most injected water along the channel to cause the invalid injection and production, for which it is hard to increase water flooding swept volume, causing flooding and high water cut well and reducing oil production. To improve the effectiveness of water injection to achieve stable yields, it is important to take the measures of ineffective injection-production wells profile control, plugging and so on for fast and accurate identifying ineffective injection-production wells. To that end, this paper applied fuzzy theory to establishing the mathematical model for identifying ineffective injection-production wells.

Abstract: Due to the differences of stress and physical property in the pay zone, the fractured horizontal well may be different in length and azimuth angle. Furthermore, because of the mutual disturbance among fractures, the accurate prediction of production of fractured horizontal wells become more complicated. This paper presents a new model to predict the production of the fractured horizontal wells by considering the effects of fracture number, fracture length, fracture interval, fracture symmetry, azimuth angle and conductivity. Compared with the numerical simulation, this model needs less parameter and calculating time, and is easy to be applied to the designs of segmentation fracturing in horizontal wells. The model in this paper has been applied to the optimizing designs of hydraulic fracturing for two horizontal wells in North China oilfield and the predicted results agree with the actual production well.

Abstract: Aiming at the cutting bed settling problems in horizontal section during drilling process, a novel additive FGC for cuttings transport is applied. The experimental results show that the wettability was converted to amphiphobic and the cuttings preferentially attached to gas bubbles after FGC adsorption on the cuttings’ surface. The surface area of the cuttings is increased and the density of it is reduced, making cuttings more easily to be driven by liquid and settlement decrease. Tested by the horizontal simulation device, the cuttings transport effect is good and most of cuttings can be circulated to the outlet position by drilling fluid.

Abstract: Stage cementing is usually applied in primary cementing in gas wells and long interval cementing. A stage tool that is free of drilling plug after cementing is a recently emerged new tool. Free of drilling of plug (DOP-free) after cementing can shorten well construction period, simplify well casing program, and then reduce rig time and drilling cost. It has the tendency to take place of conventional stage tool. But its operation reliability on DOP-free affects its extensive application in field application. In this paper, an innovative DOP-free stage cementing tool study and field application has been introduced in detail. Comparing to conventional stage tool, the specifical tool has not only operation and casing seal reliability as conventional, but also high reliability in DOP-free. Systematic tests and pilot field application indicated that it is also suitable for complicated hole cementing condition, and the DOP-free tool will substitute conventional stage tool next.