| The purpose of fracturing stimulation for high temperature high pressure deep Basalt fractural tight gas reservoir in Nanpu Oilfield is to understand volcanic rock gas concent. There is no mature fracturing stimulation technique for Basalt gas reservoir at home and abroad. The fracturing bottleneck techniques are studied suitable for formation characteristics in this paper.The following properties in Nanpu oilfield gas reservoir are:complicated rock type(Basalt), deep-seated (3880～5400m), drilling thickness volcanic rock (12～ 226m), high temperature (160～180℃), high pressure (pressure coefficient 1.31～ 1.35), low porosity(Φ=1.76～8.14%), superlow permeability(K=0.1 0.71×10-3μm2), developmenting high angle natural fracture, high Young’s modulus (50000-70000MPa), high clay mineral content (40%), high friction resistance during fracturing,limited, high leaking-off, multiple fractures, difficulty to form main fracture, so far as to operation failures,high. It is very challenged for sand fill earlier.The main research achievements of this paper are as follows:1. We finished the measurement of the rock constituents and clay mineral concent, rock mechanics parameter by simulating formation condition, and rock stress test. We calculated fracturing wells stress profile by using analysis software. The possibility law of Basalt formation fracture open and development was discussed, which provides theoretical foundation for optimization fracturing technology.2. The fracturing design and construction parameter of four wells were optimized by using Eclipse reservoir modeling software and pseudo-three-dimensional fracture modeling.3. The low friction resistance and low damage CMHPG fracturing fluid was studied, it is suitable for Basalt formation characteristics and 180℃. This system has the following features:low concentration,high temperature tolerance, low friction resistance, good carry proppant, suitable for preparing fluid water, low damage for formation rock, full break gel, easier to flowback, high fluid efficiency.4. Four well pipe manifold strcture design was studied in order to safe operation. The treatment parameter was optimized, for example pump output, ect.5. The controlling multi-fracture methods were studied for HTHP Basalt formation, which prevents early sand fill. For example, reasonable preflush percentage, multi-stage silty sand controlling fluid loss, high-viscose fluid plugging micro-fractures, small mesh proppant proportional carrying sand, aggressive proppant slug grinding and trial carrying sand, extending pumping time of low and medium sand concentration, extending pumping time during low and medium sand ratio, ect.6. The mini-frac interpretation plates for different treatment wells were established. By using G function shape analysis method, we can analyse working drawing, to acquire formation parameter in the field, and to adjust main-frac treatment parameters according to explain results, to carry out post-frac analysis.lt is to make a guide for quality control of following wells.7. The breakthrough successes of treatment were obtained by applying for fracturing auxiliary technologies. The sand fill problem was solved in Basalt gas reservoir of Nanpu oilfield. Four wells stimulation were executed successfully by 100%, the maximum amount of sand is 106m3. This study achievements afford beneficial reference for the large-frac in HTHP deep volcanic rock gas reservoir. |
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