Geological Modeling for Strong Heterogeneity of Braided Delta Reservoir: A Case Study of the Upper Triassic Formation in LN2 Test Area, Tarim Basin, Northwest China

As geological modeling on meandering river delta has been studied thoroughly, people’s attention is turning to braided delta which still have problem on characteristic its strong heterogeneous thin sand reservoir precisely.... [ view full abstract ]

As geological modeling on meandering river delta has been studied thoroughly, people’s attention is turning to braided delta which still have problem on characteristic its strong heterogeneous thin sand reservoir precisely. The paper, takes the Lower Triassic braided delta reservoir in LN2 test area for an example, propose a modeling proposal of universal significance for the strong heterogeneity braided delta reservoir which is optimal for optimize and adjust the production plan and provide guidance for similar reservoirs.
The study area has 222 wells containing 14 cored wells, and 80 wells’ history data for more than 2 decades have been collected which is significant important on verifying stratigraphic correlation and determine three-dimensional spatial distribution of sand body. The main frequency of seismic data 35HZ with a bandwidth of 5 to 55HZ and a depth about 3100 to 3350ms, covering an area about 120km2. The Huangshanjie formation braided delta outcrop, regarded as comparable to the study area, is quantitative studied to guide the scrutiny of the target area.
A combination method of object-based modeling algorithm and deterministic modeling method is involved in establishing each separate distribution bar models then contribute to the three-dimensional geological model. The key point is taking advantage of seismic information, history information and the quantitative architecture information including architectural mode, the vertical stacking patterns, and geometrical parameters of each sand bodies, which can be provided by the researches of the Huangshanjie formation outcrop analogues. The model display the structure of the reservoir and the correlation between different elements visualization which settle substantial basement for tracking the connectivity of sand bodies between wells and analyzing contributor of distribution of remaining oil.
A method of pixel-based sequential Gaussian simulation and cokriging algorithm is applied on building up reservoir property models incorporating porosity model and permeability model. On the basis of the architecture model, porosity model is setup utilizing conditional cosimulation method after variogram analysis of main and second variable with constrain of RMS attributes and impedance data from seismic inversion. Within the constraints of porosity model, combining discrete permeability data, permeability model is established with SGS. The porosity and permeability of central part of distribution bars is better, comparatively, the edges and superposition part is poorer. The result is compliance to the provenance direction that the gainful reservoir is from northeast to southwest. The further study on numerical simulation suggest that the model match the active data accurately.