| Carbonate reservoir and other types of reservoir, Acidification is the completion and production process essential to increase production measure. For the high permeability reservoir, acidizing, solution is usually used10%～20%hydrochloric acid dissolving near wellbore pollutants, and dissolution of reservoir minerals to form penetrating pollution zone of High flow channel. For the low permeable reservoirs, acid fracturing is higher than formation fracture pressure conditions, the acid and fracturing fluid into the formation, the purpose of forming artificial fracture or expansion of natural fracture, due to heterogeneity of formation and crack surface roughness differences, acid in the crack surface form non-uniform etching groove, crack closed to form a certain effective fracture length and flow of the acid corrosion fracture.The acid fracturing technology is mainly divided into ordinary acid fracturing technology and depth acid fracturing technology, ordinary acid fracturing technology routine acid fracturing technology, the utility model has the advantages of simple construction process, but as a result of acid fluid loss control, acid rock reaction speed, acid etching effect over a short distance, generally in the15m～30m. The technique is mainly suitable for damage of the hige permeability reservoir, plug block larger crack and cave reservoir. depth acid fracturing technology is to obtain longer acid etched fracture, and using different from ordinary acid-fracturing technology all acid-fracturing technology referred to as. At present, the development and application of the pad acid fracturing, multifluid acid fracturing, gelled acid fracturing, chemically retarded acid fracturing, foamed acid fracturing, emulsified acid fracturing, in-situ crosslinked gelled acid fracturing, seven of depth acid fracturing technology. The pad acid fracturing and multiple injection acid-fracturing belongs to deep acid fracturing construction using two technology, gelled acid fracturing, chemically retarded acid fracturing, foamed acid fracturing, emulsified acid fracturing, in-situ crosslinked gelled acid fracturing is different acid fluid system, and can also be used as acid fracturing technology in use, or in the pad acid fracturing and multiple injection acid-fracturing technique is selected for use.Tahe oilfield Ordovician reservoir in the Xinjiang Uygur Autonomous Region Kuche county and Luntai County, northeast from Luntai county about70km, in the northern part of the Tarim Basin in Gobi desert area, tectonic location in Shaya uplift in the Tarim Basin Cleo Cooley raised southwest slope, west of Halahatang depression, east of Caohu sag, northern Jacques, convex, snap South Shuntuoguole uplift and depression with Garr. It reveals the reservoirs are mainly developed in the lower Ordovician Yijianfang Formation, lower Ordovician, the carbonate mineral composition mainly calcite content, generally accounted for more than99%, followed by a relatively wide distribution of minerals include pyrite, silica, dolomite and authigenic quartz and so on, in addition, a part of rock containing terrigenous clastic.The Ordovician reservoir in Tahe oilfield as the matrix porosity, extremely low permeability, on the development of basic no contribution.While the fractured-vuggy reservoir distribution are mainly controlled by fissures and karst landform control, the early formation of the cave system in the late tectonic movement, long-term surface exposure and karst reconstructions and suffered severe damage.Resulting in the formation of the carbonate reservoirs in the longitudinal, transverse, very strong heterogeneity.Tahe oilfield Ordovician reservoir type belongs to the elastic displacement and elastic water drive mainly with bottom water carbonate rock karst fracture-cavity type-heavy low in saturated heterogeneous reservoir. The reservoir is in a variety of sizes ranging from a plurality of fracture-cavity system for unit composition, presence of multiple seam cavern system, multiple pressure system, oil gas water relation characteristics. Its crude oil density distribution from the east to the west is gradually increased, from the most eastern0.82g/cm3transition to the western part of the1.0g/cm3above. In this big change background and there are a number of small abnormal well area.By the comprehensive analysis of geological, karstification and later transformation function analysis, dynamic production, well test analysis, system analysis, fluid temperature and pressure distribution on the data analysis of single well in Tahe oilfield, reservoir geological model (monolayer) is mainly divided into the following categories:cave, a small cave type, fracture type, fissure filling type, matrix type. Tahe oil field of new completion are mainly natural toujing completion and acid fracturing completion in two ways. Among the new toujing natural completion rate of less than30%, acid fracturing has become the most effective measures to increase production in Tahe oil field. Conventional fractured reservoir acid fracturing fluid leakoff due to large amount of acid corrosion, artificial crack length is limited, therefore limiting communication distance of acid fracturing. With the development of Tahe oilfield blocks of expanded, reservoir development degree of variation, for wellbore distant reservoirs and small constant volume more distant favorable reservoir communication, conventional acid fracturing technology is difficult to achieve. Conventional acid fracturing has short duration of malpractice, since200928wells conventional acid pressure after flowing oil below5000t production of1-2months stopping spraying. In addition to conventional acid fracturing acid refracturing wells and natural after well completion, production for a period of time of unflowing well measures have little effect. Therefore put forward by expanding the scale of construction, improve construction displacement to achieve deep communication purpose Large scale acid fracturing technology. Large scale acid fracturing technology aimed at two categories:one category is reservoir wellbore has been associated with the reservoir connectivity, this kind of well natural completion or conventional acid fracturing completion after a period of time after production stopped spray; another kind is the wellbore and reservoir is not connected, this kind of well drill without capacity or conventional acid after pressing productivity. Large scale acid fracturing overall goal is to achieve the wellbore and favorable reservoir effective connectivity, which needs to realize the acid corrosion fracture length and acid etched fracture conductivity synchronous maximization, It is also large scale acid fracturing Technological transformation of key. By increasing the acid corrosion fracture length, so far from borehole nonproducing reservoirs and wells connected. By trying to improve the acid etched fracture conductivity solution artificial crack closure after the communication favorable reservoir and wellbore again partition problem, at the same time to achieve high yield and achieve long-term stability. This combination of carbonate reservoir in Tahe oilfield features, exploration of large scale acid fracturing mechanism, and through the development of linear gel fracturing fluid, fracturing properties of linear gum fracturing fluid carrying sand performance and maintain flow capacity indoor evaluation scale acid pressure using lead liquid; through to the Tahe the acid fluid system contrasts determined acidizing fluid formula and the optimization grouping; through to the construction, the construction scale, displacement of construction pipe column, construction organization and construction equipment evaluation, for very large scale pressure acid provides theory basis and feasible construction scheme. |
