Sandstone Gas Reservoir Commingled Gas Well Sand Sand-carrying Capacity Study

Unconsolidated sand reservoir always be buried not deep, because of it's low cementation and high content of clay and sundry, the unconsolidated rock is easy to sanding during exploitation. Sanding will lead to the damage of side wall, casing and formation. At the same time, the production of sand also erode pipeline and surface equipment and choke tubes, increasing exploitation cost. In an other side , if we don't take any measure to prevent sanding and allow the moderate sanding, although it will bring some damage to surface equipment, but it will improve the recovery rate and benefit of the reservoir. Facing the contradiction of sanding and sanding prevention, combine the practical situation of Saibei reservoir, a new exploitation manner had been put forward, that is commingling production under moderate sanding, through adjust the wellhead output to control the sand quantity, to achieve immediately and economic exploit reservoir.Contrasting the practical situation of sanding in Saibei gas reservoir, according to theoretical and experimental research on the base of investigation, draw some conclusion :(l)Combining the lithologic characteristic of Seibai gas reservoir, the sanding mechanism and influencing factor of unconsolidated sandstone had been deeply analysed , and divided the sanding mechanism into: seepage sand, week consolidated grain and matrix grains, the influencing factor including lithology, pressure wave and producing water.(2)Applying the sanding damage criteria and effective stress methods to analysis the sanding condition. From theoretical calculation, experiment test and field observe, combine the core data, the ultimate drawdown pressure of sanding in Seibai gas reservoir had been established.(3)Using the relation between stress and strain and the variation of physical property after sanding, we build the theoretical prediction model, deduce the relation between sanding quantity and radial stress, also check the model with practical production data.(4) The critical suspend condition of grain be deducted from mechanics angle, and the effects of sanding on porosity and permeability had been researched, the variation of porosity and permeability had also been analysed buy using experiment and production analysis, the sanding will bring some damage to formation.(5)Facing the problem that some gas well producing under sanding condition, the carrying sand in vertical well had been researched .The stress model of grain under different regime in well had been established, and draw the critical carrying sand velocity formulation under these different regimes. According to comparing the critical production with practical production, it seems that at present most well fulfill the request of critical velocity of carrying sand.