Production Logging of Shale Gas Well in China

SPE Annual Technical Conference and Exhibition

Zhang

et al. 2016

China is the first country achieving shale gas breakthrough outside the North America. Fuling shale gas play is one of the most successful shale gas reservoirs by far in China. However, production loggings in more than ten wells illustrate that only about one third to one half of hydraulic fractures produces. Meanwhile, the productive fractures contribute differently to the production rate. Therefore, models with non-uniform fracture properties like fracture half-length and distance between fractures are needed to model the production performance considering the production logging information. In this paper, Models with non-uniform fracture properties are built to take into the consideration of production logging results. In these models, the fractures can be with un-even distance, un-even half-length while combing specific flowing features of shale gas play like desorption, diffusion and stress dependent permeability. Production logging operations of one case well in Fuling shale gas play are reviewed. In order to honor the production logging results, Interpretation models with non-uniform facture and the ones with uniform fractures are compared. Rate and pressure transient data are used to interprete the formation permeability, fracture half-length and stimulated reservoir volume (SRV) by rate normalized pressure (RNP) method. On the basis of understanding of formation properties from rate and pressure transient analysis and non-uniform fractures properties from production logging, production rate and estimated ultimate recovery (EUR) are predicted by the models with non-uniform fractures for the case well. Results show that only about one third to one half of hydraulic fractures produces and the productive fractures have different contribution to total production rate of shale gas wells. Rate and pressure transient analysis with non-uniform fractures model gets higher formation permeability than the one with uniform fractures model. However, the fractures may have more severe interference between fractures in the non-uniform model and weaken the positive effect of higher permeability on shale gas well's production, or the dominant fractures may affect the less productive fractures adversely. Field applications show that the wells with non-uniform fractures will achieve about 21 percent less EUR than the one with equivalent uniform fractures. Production performance modeling for shale gas wells with non-uniform factures obtained from production logging is the highlight. The research may partly help the design of horizontal laterals and fractures scenarios.

Production Performance Modeling of Shale Gas Wells with Non-Uniform Fractures Based on Production Logging

SPE Annual Technical Conference and Exhibition

Zhang

et al. 2016

Pressure Transient Analysis of Shale Gas Wells With Non-Uniform Fractures

SPE Middle East Oil &Amp; Gas Show and Conference

Lei

et al. 2017

Uniform fractures with equal half-length and fracture spacing are commonly assumed when conducting pressure transient analysis and production performance estimation for shale gas wells. However, production loggings and microseismic in many shale gas wells illustrate that only about one third to one half of hydraulic fractures produces. Meanwhile, the productive fractures usually contribute quite differently to the production rate. Therefore, modeling and analyzing of non-uniform fractures properties like fracture type, half-length and fracture spacing are of great importance to understand hydraulic fractures' effect on dynamic flow regimes, pressure and production performance. In this paper, one model with non-uniform fracture properties is used combing shale gas properties like desorption, pressure dependent permeability and fracture properties like un-even distance, un-even half-length. Type-curves of interpretation models with un-uniform facture and the ones with uniform fractures are compared. Rate normalized pressure (RNP) method is used to analyze non-uniform fractures' effect on shale gas wells' flow regimes and drainage volume. Parametric analyses for five reservoir parameters and six well & fractures parameters are conducted. The reservoir parameters include reservoir permeability, porosity, pressure dependent permeability (PDP), desorption and Outer boundary area. The well and fracture parameters include clustered fracturing and evenly spaced fracturing with fixed total fracture half-length (TFH), fracture half-length, cluster spacing, cluster number per stage, stage number with fixed TFH, stage number with fixed fracture half-length. Results show that a series of flow regimes including three linear flows and three pseudo-steady state flows can be diagnosed for shale gas wells with non-uniform fractures. Three pseudo-steady state flows correspond to flow within stage volume, flow within stage plus space between stages volume, and flow within SRV separately. However, the flow regimes reflecting stage volume is missed for shale gas wells with uniform fractures. Permeability determines when the three pseudo-steady state flows happens, but doesn't change the related three volumes. Desorption doesn't change the shape of the pressure and pressure derivative curve, and it only changes the apparent drainage volume. PDP impose severe effect on shale gas well's pressure drawdown and apparent drainage volumes. Increasing the modulus results in decrease of the apparent volume being drained especially when the modulus is larger than 0.01MPa-1. Evenly spaced fracturing has lower pressure derivative and pressure drawdown than non-uniform fracturing, which means it can yield more gas production for the same amount of injected propant and fluids. Fewer stages fractures with longer half-length have lower pressure derivative and pressure drawdown, and will reach SRV boundary earlier than more stages fractures.

Comprehensive Analysis of Production Loggings in Fuling Shale Gas Play in China

Liu

SPE Middle East Oil &Amp; Gas Show and Conference

Shen

et al. 2021

Fuling shale gas field is one of the most successful shale gas play in China. Production logging is one of the vital technologies to evaluate the shale gas contribution in different stages and different clusters. Production logging has been conducted in over 40 wells and most of the operations are successful and good results have been observed. Some previous studies have unveiled one or several wells production logging results in Fuling shale gas play. But production logging results show huge difference between different wells. In order to get better understanding of the results, a comprehensive overview is carried out. The effect of lithology layers, TOC (total organic content), porosity, brittle mineral content, well trajectory is analyzed. Results show that the production logging result is consistent with the geology understanding, and fractures in the favorable layers make more gas contribution. Rate contribution shows positive correlation with TOC, the higher the TOC, the greater the rate contribution per stage. For wells with higher TOC, the rate contribution difference per stage is relatively smaller, but for wells with lower TOC, it shows huge rate contribution variation, fracture stages with TOC lower than 2% contribute very little, and there exist one or several dominant fractures which contributes most gas rate. Porosity and brittle minerals also show positive effect on rate contribution. The gas rate contribution per fracture stage increases with the increase of porosity and brittle minerals. The gas contribution of the front half lateral and that of latter half lateral are relatively close for the "upward" or horizontal wells. However, for the "downward" wells, the latter half lateral contribute much more gas than the front half lateral. It is believed that the liquid loading in the toe parts reduced the gas contribution in the front half lateral. The overview research is important to get a compressive understanding of production logging and different fractures’ contribution in shale gas production. It is also useful to guide the design of horizontal laterals and fractures scenarios design.