Advanced Materials Research Vols. 962-965

Abstract: This article presents a new exploitation method based on the same fractured horizontal well with fractures for injection or production on offshore low permeability oilfields for the purpose of adapting to their practical situations and characteristics, which means fractures close to the toe of horizontal well used for injecting water and fractures near the heel of horizontal well used for producing oil. According to proposed development mode of fracturing, relevant physical model is established, Then reservoir numerical simulation method has been applied to study the effect of arrangement pattern of injection and production fractures, fracture conductivity, fracture length on oil production. Research indicates cumulative oil production is much higher by employing the middle fracture for injecting water compared with using the remote one, suggesting that the middle fracture adopted for injecting water, and hydraulic fracture length and conductivity have been optimized. The proposed development pattern of a staged fracturing for horizontal wells with some fractures applied for injecting water and others for production based on the same horizontal well provides new thoughts for offshore oilfields exploitation.

Abstract: For small faults have great influence on remaining oil distribution and injection-production relation in the latter period of high water-cut oilfield, an accurate distribution of these minor faults is one of the main control factors of injection-production adjustment. So, the little fault location predication accurately is necessary. But, research that only rely on logging data description of fault and reservoir characteristics have certain limitation, especially in the fault-points, crosswell faults combination and extension length, plane position and continuity between wells sand body, etc. The seismic forward modeling analysis, 3D visualization, various fault classification identification describe integration technology was used, and the fine structure interpretation method was formed, which integrated technology of the first big to small, first simple to complex, slice confirm fault strike, seismic section ensure fault dip, common fixed fault attitude. Fault The remaining potential of fault nearby, crosswell sand body and enlarge transitional are developed by reunderstanding reservoir which was studied in well-seismic interpretation technology. It’s important to improve the fine remaining oil descriptiont for further increaseing understanding of reservoir and of high water-cut old oilfields.

Abstract: Reservoir with gas cap, edge water is complex. And the oil-water and oil-gas interface will seriously influence the performance. Once out of control, gas and water invasion may occur, then oil productivity will fall sharply and oil recovery will become low. In addition, the oil penetrating into gas cap would lead to oil loss. So, the controlling methods are crucial. In this paper, we study the productive characteristics of a certain reservoir with gas cap, edge water and narrow oil ring. For the phenomenon several productive wells appeared gas breakthrough and water invasion after putting into production, this paper puts up a strategy shutting in high gas-oil ratio wells and blocking off gas breakthrough layers that proved effective. At the same time, adjusting oil and gas distribution underground by gas-water alternate also be proved practicable.

Abstract: Yulin area of Changqing gas field in Ordos basin has the favorable conditions for gas accumulation in Shan 2 Member, which is the main productive layer to increase reserve and production. Based on the research of gas pool forming conditions, the distribution rules of gas in Shan 2 Member in Yulin area of Changqing gas field can be concluded: coals, swap dark mudstones and delta front sandbodies are well-developed vertically, the conditions of reservoir-forming combination for self-generation and self-preservation are processed; the sandbodies developed in submerged distributary channel and mouth bar microfacies of delta front have a high content of quartz, which have a good physical properties and a high gas production. There is a good relationship between the distribution of gas pools and the maturity of sandstone, the value 6 of maturity index (86% quartz content) can be used to delineate the zones of gas enrichment and productivity. This rule can guide the exploration and production of this area in next step.

Abstract: Zipper fracturing is becoming popular as a method that may be used to improve production performance in wells in pad drilling. Fracture network is expected in zipper fracturing, which leads to high production. The time between two consecutive stages of a horizontal well, leak-off coefficient, and pump rate have a great effect on the induced fractures, which leading to a more efficient fracture network. We will focus on the factor of time and pump rate in this paper. For the same leak-off coefficient, firstly, different initial width is calculated in different pump rate, and then with change equation is formulated from Carter’s leak off model. The stress change of different initial fracture width can be illustrated according to this model. The results show that: the bigger pump rate, the bigger initial width, which leads to a slower stress change. There is an inspiration for field zipper fracturing. Longer time between consecutive stages, that mean decrease in stress shadow, is beneficial to complex networks.

Abstract: Hydrajet fracturing connects hydraulic perforating and hydraulic fracturing together, realizing precise perforating and fracturing without packers, and it reduces the pollution to the reservoir. Initiation pressure is a very important factor during hydrajet fracturing operation. Through contrast studies of hydraulic fracturing and hydrajet fracturing, comparing their similarities and differences, analyze the initiation mechanism of hydrajet fracturing in open deviated wellbore. The derived formula of initiation pressure can help guide parameter optimization during fracturing.

Abstract: This document explains different tectonic styles and sedimentary fillings give rise to the different accumulation combinations and accumulation models between the south and the north frogs of East Subsag of South Buir Sag. The Tsagaantsav Formation oil pools, subject to the rupture of the fault-period tectonic layers, has developed multiple types of traps including reverse fault blocks, fault noses and drag anticlines. They are close to the oil-generating sags, in the indicator areas of hydrocarbon migration where hydrocarbon pools, particularly tectonic-controlled pools, are easily formed. The lithology and physical property play an important controlling role over the formation of oil pools with complicated oil-water distribution relationship. The constant and the late active ruptures as longitudinal hydrocarbon migration pathways, together with the sedimentary sands of multiple genesis types, have given shape to the multi-formation lithologic, lithologic-tectonic or tectonic accumulation combinations.

Abstract: Change confining pressure experiment or pore pressure experiment is one of the commonly used method to evaluate the reservoir core stress sensitivity. However, a large number of studies have shown that core net stress is not equal to the effective stress,the drawdown pore pressure experiment are consistent with the characteristics of oil and gas field real development process. The pressure stability of drawdown pore pressure experiment is bad, so, a reliable modified method of change confining pressure stress sensitivity experiment is eagerly expected. On the basis of the differential method principle, effective stress coefficient can be determined through core experiments,and with the use of effective stress coefficient , change confining pressure experiment is modified. Main conclusions are as follows:For sandstone core,at reservoir original stress condition with the pore pressure from 15MPa to 11MPa effective stress coefficient from 0.436 to 0.415;Based on Terzaghi effective stress exaggerate stress sensitivity, ontology effective stress can weaken the stress sensitive; Based on effective stress coefficient in this paper correction stress sensitivity is medium weak,impacts on production results almost coincident with the drawdown pore pressure test results.

Abstract: For the compression compartment safety design in gas filling station, hazards of gas explosion inside compression compartment should be assessed, and explosion energy as well as influence factors should be determined. In this paper, numerical simulation was adopted to build 3D model of compression compartment and simulate gas explosion pressure and flame propagation behavior under different ignition point location, open-pressure and weight of relief panels. The results show that the ignition point location relative to the location of the vent opening and relief panel’s characteristics is very important for gas explosion inside compression compartment. The nearer the ignition point location is away from the venting opening location, the smaller the caused explosion pressure will be. For the relief panel, explosion pressure is proportional with the open-pressure and the weight of relief panel. Besides the rational distribution of ignition source and the adoption of relief panel with less unit weight and relief pressure, the crushing material damage and secondary hazard of flame should also be noticed in order to mitigate the hazard of gas explosion.

Abstract: In order to study the effect of surfactants on wettability of quartz surface, the dynamic contact angles of different surfactants on water-wet and oil-wet quartz surfaces were measured. The experimental results showed that the advancing contact angles of cationic surfactants, anionic surfactants and nonionic surfactants on oil-wet quartz surfaces decrease with the increase of surfactant concentrations; the wettability of water-wet quartz plates remains water-wet after treated by all three kinds of surfactants. Surfactants can reverse the wettability from oil-wet to water-wet at low concentrations; The electrostatic force, hydrophobic force and the attraction between surfactant and polar components of crude oil are the key interactions in the wettability alteration process.