Pulsating fracturing, as a new technology for unconventional oil and gas exploration, enables to enhance stimulated reservoir volume (SRV) effectively, which further helps to improve well performance. It is of great importance for the evaluation of fracturing performance and optimization of fracturing parameters by accurately calculating variables from formation impairment during pulsating fracturing treatment. Based on the principle of conservation of energy, a novel theoretical model describing the evolution of rock damage was proposed by analyzing energy evolutionary characteristics from the hysteresis loop of rock stress‐strain curve while the treatment. This model was in a good agreement with experimental data. In this paper, our study indicates that the rock damage is caused by the accumulation of damage in each cyclic loading and unloading process during pulsating fracturing. Moreover, the cumulative rock damage would increase with the increment of the number of cyclic loading and unloading. Conversely, the rock strength is negatively correlated with cyclic number. The cumulative damage variable approximates to one as the rock breaks. Additionally, the frequency and the stress level of pulsating fracturing have an obvious impact on the evolution of rock damage. The optimization of these parameters can help to accelerate the rock damage and reduce the corresponding rock strength. The speed of rock damage can be accelerated with the enhancement of the stress level at the later period of the step loading, which facilitates the increment of cumulative damage variable. Our new model provides a guideline for predicting the initial rock damage during pulsating treatment.

In this paper, based on the geologic features in deepater shallow, we optimize the calculation method of the overburden pressure (four parameters regression method), pore pressure (comprehensive interpretation method), collapse pressure (Mol-coulomb criterion) and fracture pressure (pressure coefficient method) through investigation and onsite application, therefore, we can determine the safety window of mud density in shallow. Additionally, the riser setting depth is given on the basis of safe density window; Furthermore, we seek out the gradient model of the multi gradient drilling (MGD) applicable for narrow density window on the condition of simplifying casing program. An example in the South China Sea is illustrated. In the paper, we gather the geological feature and well logging data. According to the method given above, the depth of conductor is suggested. Meanwhile, compared with the safe mud window previous, the MGD gradient model can largely the thin window before as the more simple structure of well can be applied.

Deepwater drilling practice faces numbers of geological hazards which happen in shallow area due to abnormal pore pressure, and these phenomenon go worse, even affect the drilling process, combining with shallow flow, shallow gas, and gas hydrate conditions. However, applicable pore pressure calculation methods were not established in last decades. Formation pore pressure change closely with SDT, especially the reaction more obvious mudstone formation. In this paper, based on shallow soil attributes, two kinds of logging-based calculation methods are put forward. One is a comprehensive interpretation method, in which porosity, shaliness and effective stress are taken into account. The other is a multi-regression method with the consideration of P-wave velocity, affected by shallow gas velocity and shallow flow velocity, and mathematical model is established by multi-regression. Two wells in Yingqiong basin are exampled to verify above two methods. Meanwhile, calculation results are consistent with testing data, and geological hazards can be detected. Results shows that the multi-regression method is more suitable for fast prediction, and the comprehensive interpretation method is more accurate. Pore pressure calculation in deepwater is different from the shallow case due to soil attributes. How to accurately analyze it still has a long way to go. The methods proposed in this paper have been applied in many wells in the South China Sea, and provide reasonable references to drilling practice.

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Irregularly shaped electrosurgical devices face significant challenges in electrosurgery due to serious blood and tissue adhesion. Superhydrophobic surfaces inspired by lotus leaves have attracted great attention for their promising antiadhesion properties. However, there are few methods for efficiently preparing superhydrophobic irregularly shaped bipolar electrocoagulation tweezers (BETs). Herein, we propose a simple and environmentally friendly method to fabricate antiadhesion superhydrophobic surfaces on BETs. The superhydrophobicity is obtained by combining laser texturing to form rough structures and low surface energy modification via stearic acid. The formation mechanism of superhydrophobicity is investigated through analyzing microstructures and chemical compositions by scanning electron microscopy, white-light interferometry, and X-ray photoelectron spectroscopy. The functionalized BET surfaces exhibit excellent water repellency with a contact angle of 159.6°, a roll-off angle of 1°, and a surface energy of 14.3 mJ/m2, possessing excellent antiadhesion properties against blood, chicken breast tissue, and pork tissue. Compared with ordinary BETs, the mass of blood, pork tissue, and chicken breast tissue adhered to the superhydrophobic BET is reduced by 97.70, 70.34, and 75.35%, respectively. Moreover, the superhydrophobic BETs have excellent conductivity and maintain good antiadhesion properties after low-temperature storage for 2 weeks, after being impacted by sand and blood and 30 cycles of tape peeling tests. With outstanding antiadhesion performance, the superhydrophobic BET may have promising application prospects in the electrosurgery field.