电缆式地层测压资料在西湖凹陷油气田中的应用

随着西湖凹陷油气田勘探开发的不断深入,以“三低”(低电阻率/低对比度、低孔隙度和低渗透率)油气藏为主要特征的复杂油气藏所占比例逐渐增大,电缆式地层测压资料在“三低”油气藏评价中发挥着越来越重要的作用。在收集整理西湖凹陷油气田大量地层测压资料应用实例的基础上,总结了形成研究区超压的影响因素及超压点判断的方法;归纳了研究区电缆式地层测压资料的分类,测压点主要分为5大类:有效点、超压点、干点、致密点、坐封失败点;研究了电缆式地层测压资料的3类具体应用:计算地层流体密度及气油比,根据压力剖面确定流体界面,评价地层渗透率;并提出了新的油气藏气油比评价方法及流度与渗透率的转化关系。电缆式地层测压资料在储层流体性质识别及确定流体界面方面取得了较好的应用效果,对电缆式地层测压资料在西湖凹陷的后续应用具有重要的借鉴意义。

地层测压资料结合毛管压力曲线确定油水界面的方法在乌石A油田的应用

乌石A油田流沙港组三段油藏探井和评价井多处于构造高部位,很少直接钻探到油水界面,如何合理地预测油水界面位置成为勘探、评价和开发阶段的重要问题之一。传统方法利用相对渗透率曲线和毛管压力曲线预测油水界面存在诸多问题。采用地层测压资料结合毛管压力曲线方法能够较好预测油藏的油水界面,有利于开发方案的合理编制。

测井资料在井旁构造解释的应用

测井资料作为认识油气藏重要手段之一,能为油气藏井旁构造精细解释和测井沉积微相分析提供重要手段。主要介绍测井资料在井旁构造解释方面的一些应用,包括成像测井资料对过井断层的识别、地层测压资料对封闭断层的识别、判断角度不整合的地层接触关系、非轴对称背斜的判断、构造倾斜的变化趋势、地层微小错动的识别。

Fault detection based on microseismic events

In unconventional reservoirs, small faults allow the flow ofoil and gas as well as act as obstacles to exploration; for, （1） fracturing facilitates fluid migration, （2） reservoir flooding, and （3） triggering of small earthquakes. These small faults are not generally detected because of the low seismic resolution. However, such small faults are very active and release sufficient energy to initiate a large number of microseismic events （MEs） during hydraulic fracturing. In this study, we identified microfractures （MF） from hydraulic fracturing and natural small faults based on microseismicity characteristics, such as the time-space distribution, source mechanism, magnitude, amplitude, and frequency. First, I identified the mechanism of small faults and MF by reservoir stress analysis and calibrated the ME based on the microseismic magnitude. The dynamic characteristics （frequency and amplitude） of MEs triggered by natural faults and MF were analyzed; moreover, the geometry and activity types of natural fault and MF were grouped according to the source mechanism. Finally, the differences among time-space distribution, magnitude, source mechanism, amplitude, and frequency were used to differentiate natural faults and manmade fractures.

A formation pressure prediction method based on tectonic overpressure

Traditional formation pressure prediction methods all are based on the formation undercompaction mechanism and the prediction results are obviously low when predicting abnormally high pressure caused by compressional structure overpressure.To eliminate this problem,we propose a new formation pressure prediction method considering compressional structure overpressure as the dominant factor causing abnormally high pressure.First,we establish a model for predicting maximum principal stress,this virtual maximum principal stress is calculated by a double stress field analysis.Then we predict the formation pressure by fitting the maximum principal stress with formation pressure. The real maximum principal stress can be determined by caculating the sum of the virtual maximum principal stresses.Practical application to real data from the A1 and A2 wells in the A gas field shows that this new method has higher accuracy than the traditional equivalent depth method.

The Analysis of Seismic Data Structure and Oil and Gas Prediction

In this paper, a new concept called numerical structure of seismic data is introduced and the difference between numerical structure and numerical value of seismic data is explained. Our study shows that the numerical seismic structure is closely related to oil and gas-bearing reservoir, so it is very useful for a geologist or a geophysicist to precisely interpret the oil-bearing layers from the seismic data. This technology can be applied to any exploration or production stage. The new method has been tested on a series of exploratory or development wells and proved to be reliable in China. Hydrocarbon-detection with this new method for 39 exploration wells on 25 structures indi- cates a success ratio of over 80 percent. The new method of hydrocarbon prediction can be applied for: (1) depositional environment of reservoirs with marine fades, delta, or non-marine fades (including fluvial facies, lacustrine fades); (2) sedimentary rocks of reservoirs that are non-marine clastic rocks and carbonate rock; and (3) burial depths range from 300 m to 7000 m, and the minimum thickness of these reservoirs is over 8 m (main frequency is about 50 Hz).

Determining areas in an inclined coal seam floor prone to water-inrush by micro-seismic monitoring

The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor.We have used a high-precision microseismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor,especially an inclined coal seam floor,may be more accurately estimated by monitoring the continuous,dynamic failure of the floor.The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway（the lower crossheading） is deeper and that the failure range is wider here compared to the coal seam floor near the return airway（the upper crossheading）.The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified.This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine.

Study on determination method of in-situ stress using formation fracturing test and Kaiser effect method

A new method, which is based on formation fracturing test and Kaiser effect method, has been developed for confirming the oilfield in-situ stress in this paper. The new method has been used in a certain oilfield of China and the determined oilfield in-situ stresses is more accurate than that based on one single method.

Application of wireline formation tester in Tarim Oilfield

The application of wireline formation tester(WFT)gradually extends in oil-field with the constant improvement of instrument functions.Applications of WFT in oil and gas exploration in Tarim Oilfield,such as formation pressure measurement,are described,and testing efficiency between drill stem testing(DST)and WFT are compared,especially comprised of PVT sampling,hydrocarbon composition estimation,fluid characterization analysis and formation permeability analysis.The test results between WFT and traditional DST show that their functions can be complementary.The influence factors of WFT and the suitable applying conditions for WFT and DST are also discussed.