Advanced Materials Research Vols. 524-527

Abstract: Wellbore temperature is significant to well program and safety drilling for deep water drilling operations. On the basis of transient heat transfer mechanisms involved in deep water drilling among wellbore and formation and sea water, wellbore temperature profile, especially near sea bed and sensitivities to drilling fluid circulating duration, inlet temperature, water depth, water temperature, riser insulation and drilling fluid specific heat capacity have been analyzed via this model. Analysis show that deep-water wellbore temperature is much lower than a land well, the temperatures above sea bed normally ranges 10-30°C, and decreases with increased circulating duration; temperature at both outlet and bottom hole decreases drastically with increased water depth, and heat generation must be considered into estimating wellbore temperature profile especially one at bottom hole.

Abstract: Based on digital imaging processing technology, a generational method of computational grid of porous media is developed for numerical simulation. Transformation of original microscopical image from grayscale into binary one and vector-graph are used for reconstructing a geometric model of porous media. Computational grid of porous media geometry model by COMSOL Multiphysics software can provide an effective way for the latter finite element analysis of porous media.

Abstract: In Gudao Oilfield Southwest margin area, fault seal ability to determined under Guantao formation study reservoirs distribution has a very important significance. Through the research fault two plates of lithology relation, mudstone daub analysis, fault zone fillings argillaceous content analysis of the gender influence factors of study area, main fault sealing ability analysis results show that upper Guantao formation and under Guantao formation7, 8 sand formation fault seal ability is good, beneficial to the forming reservoirs; Under Guantao formation8 sand formation the following fault seal ability is bad, and can be used for oil and gas migration channels.

Abstract: Improved optimization of drilling bit selection and the compatibility between drilling bit and formation constraint the ROP and cost of deep well drilling to some extent. This combined with lab comprehensive lab drilling simulations and mechanisms of rock penetration can hold promise for improving drilling efficiency in deep wells. This paper reviews the mechanical characteristic parameters of rock engineering and demonstrates the obstacle of rock penetration in deep wells. Based on the general predictable formula of ROP, the relationship between drilling sensitive index and formation drillability is analyzed and the optimization and optimal match of drilling technology parameters are described. Technology Benefit Index (TBI) is proposed to evaluate the technical performance of drilling bit, advices and warnings from lab experiment and field experience on selecting and using bit are put forward. Statistical analysis of Well A based on TBI is made, the analysis of ROP improvement potential and overall program (including Bottom Hole Assembly, drilling parameters and type of drilling bit) of ROP improvement for Well B are worked out. Suggestions of drilling bit using based on mechanisms of rock penetration are proposed. Guided by the theory on improving ROP field tests of improving drilling rate are conducted to examine the field performance. By comparison, the tested sections yield high performance of ROP improvement. The designed program enhancing ROP for experiment section proves to be operable and shows great promise in further improvement and application.

Abstract: With superheated steam, there is no direct relationship between temperature and pressure, Therefore, at a particular pressure it is possible for superheated steam to exist at a wide range of temperatures higher than that of its saturated steam. The heat transfer coefficient is 1/150-1/250 as much as that of saturated steam during heat transferring, and it takes a relatively long time to cool, during which time the steam is releasing very little energy and transmitted long distances. The mechanisms of superheated steam stimulation are mainly pointed to the performance of crude oil viscosity reduced, flow environment improved, rock wettability changed, oil displacement efficiency improved. Physical simulation shows that oil displacement efficiency by superheated steam is 6-12% higher than that of saturated steam at the same temperature, and under the condition of carrying the same heat, superheated steam enlarged the heating radius by about 10m, oil steam ratio increased by 0.7. Superheated steam stimulation was put into Kazakstan’s heavy oil reservoir after two cycles of saturated steam stimulation. The average daily oil production was 2-4 times that of saturated steam stimulation, which improved heavy oil production effectively. The secondary heavy oil thermal recovery by superheated steam stimulation applied in marginal heavy oil reservoirs achieved satisfactory effect.

Abstract: The inflow performance prediction is very important to completion optimization of slanted wells. A reservoir/wellbore coupling model for slanted wells in anisotropic parallelepiped reservoirs considering wellbore pressure drop is presented based on source function method and superposition principle and solution methodology is described. On this basis, the inflow behavior of a slanted well in an anisotropic, infinite slab reservoir with impermeable top and bottom boundaries is investigated. Potential drop in the wellbore can cause flux difference, which is greatest under isotropic, and decreases with vertical anisotropy. Well productivity decreases with vertical anisotropy and the decrease is more significant for larger inclination angles than for smaller ones. Well inclination angle has a greater influence on inflow performance of wells in higher-anisotropy reservoirs than in lower-anisotropy ones and should be determined cautiously in the reservoir engineering design.

Abstract: For the existence of formation water, the capillary force increases when the gas flow in the cores, so the flow may display starting pressure gradient. However, during the lab testing, sometimes it is found that the starting pressure gradient changes in different test conditions: when the outlet pressure is atmosphere, only the water saturation reaches critical value (Sw)_c, the quasi starting pressure exists; but when the outlet pressure is not atmosphere; it is easy to find the quasi staring pressure in the same water saturation. And the quasi starting pressure under the later condition is larger than that in former condition. It is also found that the quasi starting pressures are both power function to the ratio of core coefficient and water saturation. The experimental results provide some theoretical references for recognizing the flow characteristics in low permeability gas reservoirs.

Abstract: Installation is the key technology of the deepwater vertical collet connectors. Based on thorough analysis of the existing installation technology and construction resources, combined with the technical features of installation used to connect different types of jumpers, new designs of vertical collet connectors installation for rigid jumpers and flexible jumpers are proposed in detail in this paper.

Abstract: A type of Q125 grade high-strength low carbide oil tube steel was designed and researched. The strengthening mechanism of the steel was analyzed by SEM and TEM, and the CO2 corrosion behavior of the steel was simulated by high-temperature and high-pressure autoclave. The result show: the size of original austenite grain, packet and block are about 10-15μm, 2μm and 200nm, respectively, so the strength of the steel matched toughness well. The precipitate of (Nb,Ti)(C,N) whose size is about 60nm can restrain coarsening of the original austenite grain through pitting austenite grain boundary; The precipitate of (Nb,Ti)C and nanometer sized precipitate of NbC can be an effective barrier for dislocation motion, so that has great contributions to improve the strength of the steel. The average and pitting corrosion rate increased first and then dropped down with the increasing of temperature. There is a maximum of average and pitting corrosion rate at 90°C; Simultaneously, when the temperature is 90°C, there is a biggest difference between average corrosion rate and pitting corrosion rate.

Abstract: This paper will take the complex layer of the Qunkuqiake region of Tarim Basin as a research object in order to find the reasons of the borehole instability. The layered drilling fluid design technique is put forward firstly and a new drilling fluid technology to solve the problems of wall instability of the Qunkuqiake regions in Tarim Basin is developed.