Simulation of unconventional well tests with the finite volume method

The finite volume method has been successfully applied in several engineering fields and has shown outstanding performance in fluid dynamics simulation. In this paper, the general framework for the simulation ofnear-wellbore systems using the finite volume method is described. The mathematical model and the numerical model developed by the authors are presented and discussed. A radial geometry in the vertical plane was implemented so as to thoroughly describe near-wellbore phenomena. The model was then used to simulate injection tests in an oil reservoir through a horizontal well and proved very powerful to correctly reproduce the transient pressure behavior. The reason for this is the robustness of the method, which is independent of the gridding options because the discretization is performed in the physical space. The model is able to describe the phenomena taking place in the reservoir even in complex situations, i.e. in the presence of heterogeneities and permeability barriers, demonstrating the flexibility of the finite volume method when simulating non-conventional tests. The results are presented in comparison with those obtained with the finite difference numerical approach and with analytical methods, if possible.

Biochemically curative surgery for gastrinoma in multiple endocrine neoplasia type 1 patients

AIM： To search for the optimal surgery for gastrinoma and duodenopancreatic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1. METHODS： Sixteen patients with genetically confirmed multiple endocrine neoplasia type 1 （MEN 1） and Zollinger-Ellison syndrome （ZES） underwent resection of both gastrinomas and duodenopancreatic neuroendocrine tumors （NETs） between 1991 and 2009. For localization of gastrinoma, selective arterial secretagogue injection test （SASI test） with secretin or calcium solution was performed as well as somatostatin receptor scintigraphy （SRS） and other imaging methods such as computed tomography （CT） or magnetic resonance imaging （MRI）. The modus of surgery for gastrinoma has been changed over time, searching for the optimal surgery： pancreaticoduodenectomy （PD） was first performed guided by localization with the SAST test, then local resection of duodenal gastrinomas with dissection of regional lymph nodes （LR）, and recently pancreas-preserving total duodenectomy （PPTD） has been performed for multiple duodenal gastrinomas. RESULTS： Among various types of preoperative localizing methods for gastrinoma, the SASI test was the most useful method. Imaging methods such as SRS or CT made it essentially impossible to differentiate functioning gastrinoma among various kinds of NETs. However, recent imaging methods including SRS or CT were useful for detecting both distant metastases and ectopic NETs; therefore they are indispensable for staging of NETs. Biochemical cure of gastrinoma was achieved in 14 of 16 patients （87.5%）; that is, 100% in 3 patients who underwent PD, 100% in 6 patients who underwent LR （although in 2 patients （33.3%） second LR was performed for recurrence of duodenal gastri- noma）, and 71.4% in 7 patients who underwent PPTD. Pancreatic NETs more than 1 cm in diameter were resected either by distal pancreatectomy or enucleations, and no hepatic metastases have developed postoperatively. Pathological study of the resected specimens revealed co-existence of pancreatic gastrinoma with duodenal gastrinoma in 2 of 16 patients （13%）, and G cell hyperplasia and/or microgastrinoma in the duodenal Brunner＇s gland was revealed in all of 7 duodenal specimens after PPTD. CONCLUSION： Aggressive resection surgery based on accurate localization with the SASI test was useful for biochemical cure of gastrinoma in patients with MEN 1.Imamura Metal. Curative resection of gastrinoma in MEN-1

Risk assessment of fault water inrush during deep mining

With the gradual depletion of shallow coal resources,the Yanzhou mine in China will enter the lower coal seam mining phase.However,as mining depth increases,lower coal seam mining in Yanzhou is threatened by water inrush in the Benxi Formation limestone and Ordovician limestone.The existing prediction models for the water burst at the bottom of the coal seam are less accurate than expected owing to various controlling factors and their intrinsic links.By analyzing the hydrogeological exploration data of the Baodian lower seam and combining the results of the water inrush coefficient method and the Yanzhou mine pressure seepage test,an evaluation model of the seepage barrier capacity of the fault was established.The evaluation results show the water of the underlying limestone aquifer in the Baodian mine area mainly threatens the lower coal mining through the fault fracture zone.The security of mining above confined aquifer in the Baodian mine area gradually decreases from southwest to northeast.By comparing the water inrush coefficient method and the evaluation model of fault impermeability,the results show the evaluation model based on seepage barrier conditions is closer to the actual situation when analyzing the water breakout situation at the working face.

Experimental research on hydrophilic characteristics of natural soft rock at high stress state

In order to study features of rock–water interaction, a self-developed experimental system called Intelligent Testing System for Water Absorption in Deep Soft Rocks(ITSWADSR) was utilized to analyze the hydrophilic behaviors of natural soft rock at high stress state. Combining X-ray diffraction and mercury injection test, main influencing factors on hydrophilic characteristics were studied. According to the results, it could be concluded as the following:(1) the effective porosity, and the content of illite, illite/smectite formation(S = 5%) and kaolinite have positive correlation with the water absorption capacity of rock; meanwhile, the initial moisture content, fractal dimension of effective pores, illite/smectite formation(S = 30%) and chlorite present negative correlation;(2) among the positive factors, the ascending order is kaolinite, illite/smectite formation(S = 5%) and illite;(3) the descending order among the negative factors are chlorite, illite/smectite formation(S = 30%) and fractal dimension of the effective pores;(4) influence of effective porosity on the pressurized water absorbing capacity of rock is minimal, while it is maximal in the process of no pressurized water absorption.

Theory and application of the transient injection well test

Based on the theory of the pumping well test,the transient injection well test was suggested in this paper.The design method and the scope of application are discussed in detail.The mathematical models are developed for the short-time and long-time transient injection test respectively.A double logarithm type curve matching method was introduced for analyzing the field transient injection test data.A set of methods for the transient injection test design,experiment performance and data analysis were established.Some field tests were analyzed,and the results show that the test model and method are suitable for the transient injection test and can be used to deal with the real engineering problems.