Study On Recovery Of Both Gas And Water In Water-bearing Carbonate Gas Reservoir

Moxi Gas Field T1j2gas reservoir was found in the late1970s by moshenl well and moshen2well, when drilled in the region T1j2good gas showed. By the early1990s,10prospecting wells was drilled with intended interval T1j2, and got good gas shows and oil test. From2003on, exploratory wells and development wells were drilled successively, Moxi Gas Field T1j2gas reservoir came into full scale development. Currently the gas reservoir was studied less. This reservoir is water-bearing tight, reservoir heterogeneity is strong, gas-water relation is complex. There is no uniform gas-water interface. Gas wells produce water commonly, and water production is quite different. The gas reservoir characteristics are typical, which does not have edge water or bottom water usually, also has not relative water-rich area, in order to achieve a reasonable and efficient development, so that the gas reservoir was selected for the study.From2003to2013the development history proved that the early gas and water layer logging interpretation need to be adjusted. Gas reservoir connectivity is unclear, gas and water distribution and controlling factors is not clear as well. Gas layer、 gas-water layer and water were all shot, gas and water were producing by a single oil tube, as a result that gas production and water production changed complexly, even a few well produced too water and effected gas production.Since water production mechanism is unclear, and lacks of a clear understanding of the source of water production, water production can not be accurately predicted, no fitting draining gas exploitation technology measures was conducted.Based on previous research on the geological understanding of the region, having fully integrated logging, mercury, oil testing, formation water chemistry and production etc. static and dynamic information, and being leaded by theories such as logging geology, oil field water chemistry, the development of geology, oil and gas seepage mechanics, oilfield chemicals, natural gas engineering theory, this paper studied gas water relation, analyzed well producing by single oil tube with open water layer, optimized foam scrubbing agent. This paper obtained the following achievements and understandings: 1. By integrated use of all the information in the study area, accessed lithologic log response range and reservoir logging demarcation, log interpretation influencing factors were analyzed, gas-water layer logging interpretation cross plots were drew, and gas-water layer multiple regression discriminant equations were established. The cross plots and equations works well.2. By analysis of the gas reservoir dynamics, found that gas AOF is low, productivities’difference is big; T1j2is principal producing formation; South structure mainly distributes wells with high tested productivity and good production; high capacity well relates to effective thickness; initial reservoir pressure was high, but the pressure drops quickly; water production varied hugely.3. By formation water chemical analysis, found that the total salinity distribution in the study area was between1420-103560mg/L, mainly distributed within40-80g/L. During production some wells’salinity, ionic content and chemical characteristics parameters changed, indicating changes of water source. In the study area CaCl2water type was main, in central east T1j2Na2SO4water type exists. In Na2SO4water type area, coefficient of desulfurization is high, combined with other factors, found that under compaction aqueous gypsum became anhydrite, at the same time bled much water with sulfate to formation water system, changing CaCl2water type to Na2SO4water type.4. Gas-water connectivity was analysed, found that there is no uniform gas-water interface, water was mainly from the air-water layer and water body. T1j2A, T1j2C and T1j23are mainly gas layers. T1j21and T1j2B are mainly gas-water layers, and some water body. Water bodies were classified to4types, such as edge water, bottom water (can be divided to "isolated" bottom water and dispersed bottom water),"isolated" water and gas reservoir "residual water". Gas and water distribution controlling factors were also analysed.5. The various water production characteristics were summarized, and having analyzed the corresponding geological model. Through the analysis of various types of water production mechanism, found that when gas-water layer produced if water/gas ratio remained stable, the production could be maintained. Bottom water would raise water/gas ratio, and decrease gas production. Single oil tube is not suitable to produce if water was shot.6. For the model, that upper layer is gas-water, lower is water layer, gas-water critical mass flow and analytical expression of the interface shape between gas-water layer and water layer were derived. 7. Based on existing slice mining, which produces gas by casing tubing annulus, water by oil tube, double oil tubes for slice mining was put forward. For the model, that upper layer is gas, lower is water layer, gas and water production relational expression was derived. Relational expression between mass flow and water production was also derived for the model, which upper layer is gas-water, lower is water layer.8. Enhancing foam properties and patterns by nanomaterials was studied.This high-performance foam was introduced to foam drainage gas processing agent. According to the formation water and gas nature in Moxi gas field T1j2reservoir, experiments were carried. This foam showed good drainage effect.