Degree Of Reserve Recovery Research Articles

Reserve evaluation of high pressure and ultra-high pressure reservoirs with power function material balance method

It is difficult to determine the effective reservoir rock compressibility, aquifer volume and water influx of high pressure and ultra-high pressure gas reservoirs, so when the traditional apparent reservoir pressure and cumulative gas production curve extrapolation method and its modified version are used to calculate the initial gas in-place of such gas reservoirs, the calculation accuracy is lower. The material balance equation in the form of power function for such gas reservoirs was established based on Gonzalez method to improve the accuracy and reliability of reserve evaluation. Then, based on 20 high pressure and ultra-high pressure reservoirs that had been developed abroad, the empirical value of the power exponent was defined, and the influences of the depletion degree of apparent reservoir pressure and the degree of reserve recovery on the reliability of reserve calculation were analyzed. Besides, the critical value of the key parameter affecting the reliability of reserve evaluation (depletion degree of apparent reservoir pressure) was determined and compared with the critical value of the two-linear trends. Finally, an example calculation was carried out. And the following research results were obtained. First, the empirical value of the power exponent calculated using the material balance method in the form of power function is 1.02847, with an upper limit of 1.11567. Second, the depletion degree of apparent reservoir pressure corresponding to the inflection point of the classical two-linear trends ranges from 0.14 to 0.38 with an average of 0.23, while that corresponding to the extrapolation point of the second straight line is between 0.23 and 0.50 with an average of 0.33, and the corresponding degree of reserve recovery is in the range of 33%–65% with an average of 45%. Third, the reserves of such high pressure gas reservoirs calculated with this new method has an error rate less than 10% if the depletion degree of apparent reservoir pressure is greater than 0.33. In conclusion, for such high pressure gas reservoirs and the stress-sensitive fractured gas reservoirs, the material balance method in the form of power function proposed in this paper can avoid the uncertainty parameters (e.g. effective reservoir rock compressibility, aquifer volume and water influx) and it is advantageous with simple calculation process, better practicability and small error.

Well type and pattern optimization method based on fine numerical simulation in coal-bed methane reservoir

Coal-bed methane (CBM) is a precious clean energy. A reasonable well type and pattern design is the premise and the key to effective development of coal-bed methane. In this paper, a set of optimization method is presented which includes a fine CBM numerical model with the combina tion of the isothermal adsorption test results. Different Langmuir curves and adsorption–desorption time are corresponding to different grids in the model. The model has advantages over previous models in terms of the CBM reservoir structural characteristics and permeability anisotropy. As in most of CBM mining area, the structural characteristics are so complex that a combination of vertical and U-shaped wells is the best choice to achieve optimum production of gas. To optimize the pattern and spacing between vertical wells, different types of coal-bed cleats pressure drop rules are in consideration. Based on the CBM content in the reservoir, the distribution of different well types can be determined. The optimization method above has been applied in one pilot area in QinDuan Block, China. The result shows that combination of U-shaped and vertical wells in a diamond well pattern will provide the best CBM production scenario. In this diamond well pattern, the optimum well spacing along the long and short diagonals is 350 and 300 m, respectively. The degree of reserve recovery was predicted to up to 56.63 % after 30 years of production.

A Study on Factors Influencing the Effect of CO<sub>2 </sub>Flooding in F48 Block

Using the Eclipse software to establish the component numerical simulator of formation crude, this paper analyzed the factors that influence the effect of CO2 flooding, including permeability, the crude oil relative density, the inlayer heterogeneity, interlamination heterogeneity, intrastratal cross flow channel and so on. The results show that along with the increasing of the permeability, the degree of reserve recovery of CO2 flooding enlarged, and with the increasing relative density of the crude oil, the degree of reserve recovery of CO2 flooding decreased. The stronger of the inlayer heterogeneity and the interlamination heterogeneity, and the higher of the permeability of the cross flow channel is, the lower level of CO2 flooding degree of reserve recovery it tends to be.

A Study on Influence Factor of Steam Flooding Development Effect in Heavy Oil Reservoir

Steam flooding is an important method to improve the recovery factor heavy oil. Produce energy would consume a certain amount of crude oil in steam flooding; as a result, the evaluation of development effect of steam flooding should consider not only the degree of reserve recovery but also the heat utilization. In this paper, through the analysis of the mechanism of steam flooding, using reservoir engineering and numerical simulation methods, research the deposition, strata dip, steam injection rate, steam quality, production injection ratio and well completion method on the impact of steam flooding development effect in heavy oil.

The Field Test about CO<sub>2</sub> in Low Permeability Oilfield of Daqing Outskirt

Note CO2 gas development has become a very effective reservoir mining method in low permeability oilfield of Daqing outskirt. It can effective enhance the recovery ratio. When the crude oil dissolves CO2, the volume expands and the viscosity decreases. Under the same conditions of temperature, expansion increases with pressure, CO2 drive is more effective than a single water drive, the degree of reserve recovery has been significantly improved, generally 1.3-1.4 times. Field tests shows that the input-output ratio in swallowing- spitting test of CO2 producing in formation could reach 6.25.

The Research of Flood Pattern Completeness in the Thin and Poor Oil Layers of South West II Area

As line well pattern is the main development technique in the thin and poor oil layers of Daqing Oilfield South West Ⅱ PⅠ group, the layers have been idle and the degree of reserve recovery is far less than the region level. In response to these problems, we analyzed the balanced flood performance of various layers and the remaining oil distribution through numerical simulation technique. It shows that, the main remaining oil type of intended layers is caused by voidage-injection imperfection. Considering the needs of the follow-up infill well pattern and tertiary oil recovery, we decided to keep the well network independent and integrated without disturbing the pattern configuration and main mining object of various sets of well pattern. Finally we confirmed to perforate-adding the first infill wells of intended layers to consummate the water flooding regime. Through analyzing the production target of different well pattern optimization programs relatively, it shows that the best program has regular well pattern and large drilled thickness.

The Influence Factors of Numerical Simulation on CO<sub>2</sub> Flooding in F-48 Block Low Permeable Oil-Field

In order to enhance the oil recovery of low permeable oil-field, this paper uses the Eclipse software to establish the component numerical simulator of formation crude, analyzes the factors that influence on CO2 flooding, such as permeability, the crude oil relative density, the inlayer heterogeneity, interlamination heterogeneity, intrastratal cross flow channel and so on. The results show that along with the increasing of the permeability, the degree of reserve recovery of CO2 flooding enlarged, and with the increasing relative density of the crude oil, the degree of reserve recovery of CO2 flooding decreased. The stronger of the in layer heterogeneity and the interlamination heterogeneity, and the higher of the permeability of the cross flow channel is, the lower level of CO2 flooding degree of reserve recovery it tends to be. The light reservoir which with poor development in vertical permeability or in the thin oil layers should be selected to use the CO2 flooding, in order to guarantee a better development effect on the low permeable oil-field.

A Quick Evaluation Model for Horizontal Well Development in Bottom Water Reservoir

The evaluation model for horizontal well development has significant potential in recoverable reserves uncertainty studies. This paper firstly establishes an evaluation model on the degree of reserve recovery at different level of water cut, and then makes a chart of the dimensionless aspect seepage ratio against the degree of reserve recovery at different level of water cut. Secondly, introduces heterogeneity correction factor and saturation correction factor to improve the oil recovery model. Finally, the oil recovery of 6 reservoirs with horizontal well development in Dagang Oil Company indicates that the prediction of the evaluation model is agreement with the actual data, and the model can provide criteria for horizontal well development in a bottom water reservoir.

Method for calculating production indices of multilayer water drive reservoirs

Based on the dual-phase unstable flow theory of oil and water, the production indices calculating method of multilayer water drive reservoirs are established, which takes the changes of rock permeability and oil viscosity into consideration. The flowing resistance and production pressure drop of every sublayer is taken as the weighting coefficient in the allocation of well productivity. The solution of pressure equation is obtained by the implicit difference equation. And the water saturation is calculated by the streamline model, which enhanced the stability of solution. Using this model the production indices such as water cut and the degree of reserve recovery can be calculated for the development unit of multilayer reservoir at different development stage. The calculation method is applied into field example and the result shows the good agreement with the actual case. This research provides an important measure for the optimization of layers recombination modes.