Great Promise for Coal-derived Gas Exploration in China

With the introduction, development and application of coal-derived gas geological theory, China’s coal-derived gas exploration has witnessed a rapid development, and the theory gave an enormous impetus to robust growth of natural gas reserves and rapid development of natural

Discussion on rheology in petroleum and nature gas teservoir stimulation

Petroleum and nature gas not only are important resources,but also are important strategic materials of our country.All methods the enhancing the producing degree of petroleum and natural gas reservoir,increasing single well production and extending the stimulation period of validity are important stratagem for petroleum and natural gas exploitation.Fracturing and acidizing are the main methods for stimulation as well as one of representative examples of rheology theory application in engineering.Based on analysis of low permeability reservoir characteristics,the fracturing and acidizing stimulation principles and main controlling factors were discussed.And the mechanical characteristics,chemical reaction and rheological behavior in the stimulation process were reviewed.Furthermore research trends afterwards including the material and fluid rheology in oil and natural gas production process,the deep rock fracture initiation and extension rheology,and the fracturing and acidizing application rheology were also proposed in this paper.

Numerical Simulation Research on Energy Supplement of Low Permeability Reservoirs with Fractured Horizontal Wells

The fractured horizontal wells are widely used in many large oil fields to enhance oil recovery.Currently most of fractured horizontal wells were developed in elastic recovery.It is urgently needed to supply formation energy because of the fast production and pressure decline.In this paper,a five-spot model of horizontal wells was built based on the Jilin Oilfield geological data from the horizontal wells demonstration area.Compositional simulation were applied to study on the effectiveness of four development methods for three types of low permeability reservoirs with fractured horizontal wells and the impact of the distribution of the fracture was analyzed.Reasonable suggestions were proposed for three types of low permeability reservoirs from two aspects,development mode and fracturing design.This paper will provide some guidance for fractured horizontal well development.

Meso-Cenozoic Tectonic Events Recorded by Apatite Fission Track in the Northern Longmen-Micang Mountains Region

There is a cross-cutting relationship between the E-W trending structures and the NE- trending structures in the northern Longmen-Micang Mountains region, which reflects possible regional tectonic transition and migration. Apatite fission track （AFT） analyses of 15 samples collected from this area yield apparent ages varying from 30.3±4.2 Ma to 111.7±9.0 Ma and confined-track-lengths ranging from 10.6±0.3 pm to 12.4±0.1 μm. Four specific groups were identified on the basis of the Track Age Spectrum Calculation （TASC） patterns, i.e., 143-112 Ma, 93.6-88 Ma, 42-40 Ma and -25.6 Ma. These age groups correspond to the spatial distributions of datasets and may represent four tectonic events. Together with the regional deformation patterns, the four age groups are interpreted to indicate tectonic superposition, transition and migration during the Meso-Cenozoic with the following possible order： （1） the Micang Mountains belt was dominated by the E-W trending structure during 143-112 Ma; （2） the contraction of the Longmen Mountains belt from the NW to the SE during 93.6-88 Ma led to the superposition of the NE-trending structures over the E-W trendinding structures; （3） dextral strike-slip shear dominated the Longmen Mountains belt at 42-40 Ma; （4） westward migration of the active tectonic belt occurred from 93.6-25.6 Ma in a break-back sequence in the northern Longmen Mountains belt. The Late Cenozoic tectonics in the northern Longmen Mountains belt are characterized by the dextral strike-slip shear and the occurrence of westward break-back sequence of deformations. As a result, north-south differences in deformations along the Longmen Mountains belt were intensified since the Miocene time and strains were mainly accumulated in the hinterland of the Longmen Mountains instead of being propagated to the foreland basin.

Water coning mechanism in Tarim fractured sandstone gas reservoirs

The problem of water coning into the Tarim fractured sandstone gas reservoirs becomes one of the major concerns in terms of productivity, increased operating costs and environmental effects. Water coning is a phenomenon caused by the imbalance between gravity and viscous forces around the completion interval. There are several controllable and uncontrollable parameters influencing this problem. In order to simulate the key parameters affecting the water coning phenomenon, a model was developed to represent a single well with an underlying aquifer using the fractured sandstone gas reservoir data of the A-Well in Dina gas fields.The parametric study was performed by varying six properties individually over a representative range. The results show that matrix permeability, well penetration(especially fracture permeability), vertical-to-horizontal permeability ratio, aquifer size and gas production rate have considerable effect on water coning in the fractured gas reservoirs. Thus, investigation of the effective parameters is necessary to understand the mechanism of water coning phenomenon. Simulation of the problem helps to optimize the conditions in which the breakthrough of water coning is delayed.

Reaction mechanism and kinetics of pressurized pyrolysis of Chinese oil shale in the presence of water

A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.

New method for plugging channeling in oil field by nitrogen foam

In order to present a new method for plugging channeling in oil field,the injection modes and validity period of foam system which plugged the formation water layer were studied by means of the experimental model which simulated the real conditions of oil wells existing channeling.Above all,the influence factors including reservoir pressure,permeability,oil saturation and gas-to-liquid ratio were studied through dynamic experiment.Then,in light of the technology characteristics of foam injection in oil field,the comparison between gas-liquid and liquid-gas injection modes was studied.The result shows that the gas-liquid injection mode can ensure the foam injectivity and plugging performance.The plugging validity of nitrogen foam injected into the formation water layer was evaluated in different plugging pressure gradients by the dynamic method which is more reasonable than the static evaluation method in laboratory.The research demonstrates that the plugging validity period of foam decreases with plugging pressure gradient increasing.If the plugging pressure gradient is 0.15 MPa/m,the validity period is 160 h.Finally,a empirical equation and a plate about the plugging validity and the plugging pressure gradient were obtained for forecasting the validity period of foam.

Current Situation and Outlook of CBM Industry in China

Current situation of CBM industry in China China is abundant in CBM with a resource buried shallower than 2000 meters of 36.81 tcm and recoverable resource of 10.87 tcm. This resource base is favorable

Numerical study on the deformation of soil stratum and vertical wells with gas hydrate dissociation

Gas hydrate（GH） dissociates owing to thermal injection or pressure reduction from the well in gas/oil or GH exploitation. GH dissociation leads to, for example, decreases in soil strength, engineering failures such as wellbore instabilities, and marine landslides. The FLAC3 D software was used to analyze the deformation of the soil stratum and vertical wells with GH dissociation. The effects of Young＇s modulus, internal friction angle, cohesion of the GH layer after dissociation, and the thickness of the GH layer on the deformation of soils were studied. It is shown that the maximum displacement in the whole soil stratum occurs at the interface between the GH layer and the overlayer. The deformation of the soil stratum and wells increases with decreases in the modulus, internal friction angle, and cohesion after GH dissociation. The increase in thickness of the GH layer enlarges the deformation of the soil stratum and wells with GH dissociation. The hydrostatic pressure increases the settlement of the soil stratum, while constraining horizontal displacement. The interaction between two wells becomes significant when the affected zone around each well exceeds half the length of the GH dissociation zone.