The tight sand oil reservoir found in the Ordos basin is known for its very low porosity and permeability. Almost every well has been stimulated using hydraulic fracturing techniques. The average production for a vertical well is approximately 4–5 tons per day. Among such a large number of fracture jobs, enhanced production after stimulation does not always meet expectations. Since2005, hydraulic fracturing monitoring services have been carried out widely in this field to improve fracture geometry understanding and optimize well placement. With the implementation on-site, real-time hydraulic fracture monitoring, the pumping procedure can be adjusted accordingly based on the mapped microseismic events. Based on the past hydraulic fracturing monitoring experience in this field, an average microseismic event detectable distance range around 300 m is expected for the case of geophones inside a monitor well. Two parallel horizontal wells were thus drilled at 600m apart. Horizontal section length is around 1,500m for both wells. The original hydraulic fracture plans for each well consisted of 18 stage stimulations, but were subsequently adjusted to 13stages based on real-time hydraulic fracture monitoring results. Three monitoring wells were drilled from toe to heel as shown in Figure 1. These monitor wells will also be used as water injection wells in later secondary recovery processes. So hydraulic fractures generated by the pumping from both horizontal wells are not expected to extend far enough to reach the monitor wells. With this favorable well layout, simultaneous dual-well hydraulic fracture monitoring was proposed and conducted. In order to obtain the optimized fracturing parameters first, the initial 3 stages of each treatment well was conducted at one stage per well i.e. stimulate well-1 and then move to fracwell-2. Simultaneous hydraulic fracturing began after the initial six stages were completed.

The world's first offshore production test of the methane hydrate (MH) project was successfully carried out in the deepwater Nankai Troughin 2013. In February and March 2012, a production well and two monitoring wells were drilled and cemented to deploy temperature monitoring systems for which a combination of distributed temperature sensing (DTS) and array-type RTD (Resistance Temperature Detector) was employed.For cement hydration, the chemical reactions are exothermic in nature so that a measureable temperature increase will be observed once the heat is released. With a typical cement system in wellbore configuration, this temperature increase could result in MH dissociation prior to the production that may have some impacts on the extraction of actual methane gas. Additionally, potential problems of thermally induced cracking are another concern.To evaluate the thermal effect from the cement heat to MH, a 1D numerical model of cement hydration is developed based on the radial heterogeneity of thermal properties. The temperature data acquired during cementing stage is used as the input data for the model, and the parameters such as activation energies for the cement hydration heat correlation in the model are determined. It was shown that the variation of simulated temperature from different MH saturation within the upper MH zone is so small that a reliable estimation of MH saturation becomes difficult while the estimated MH saturations from temperature data inversion in the lower MH zone are relatively high. A sensitivity study is also performed to understand which parameters in the developed model most significantly influence the temperature during the different stages of the cement hydration, respectively.