Improvement Of The Potassium Sulfonate Drilling Fluid

Daqing peripheral oil field presents the following characteristics such as oil sheet, fewer zones, bad reservoir nature, low reservoir abundance. When this kind of oil field was exploited, it is critical to protect reservoir, especially for the well drilling process. The drilling fluid available in Daqing can cause damage to the reservoir. So it is important to develop a kind of technology measure which can prevent the reservoir damage when drilling the low permeability layer. The potassium sulfonate drilling fluid which suits well drilling technology of the peripheral oil field is studied. The affects that the potassium sulfonate drilling fluid exercises on the flow efficiency are evaluated.Through the laboratory experiments, the improved potassium sulfonate drilling fluid formulae is bentonite 5%, 0.4%Na2CO3, 1.5% K2SO4, 1000mg/LDCL, 100mg/LDesco. The funnel viscosity less 70s, filtration loss less 26mL, density less 1.15g/cm 3, K+concentration 12000～20000mg/L. The recovery of drilling fluid system is raised by more than one time than do in the fresh water. The 24h static swellable rate is 1.11%,while 28.6% in the fresh water. It indicates the drilling fluid can exercises excellent antiswelling performance on the bentonite. The loss factor of the same weight of shale soaked in the sulfonate drilling fluid is 2.8%, while 6.9% in the fresh water. It indicates that the sulfonate drilling fluid has better ability to prevent the shale from swelling.Core simulating experiments demonstrate that the solid phase in the drilling fluid can enters the void of the natural core with little amount of solid phase concentrating on the front of the cores. It can form the mud cake resulting the invasion depth less 5.0cm. The sulfonate drilling fluid to some extent can cause damage to the core permeability. The time is longer, the worse damage is. However, the damage ration is usually less 30%. The main mechanism of the sulfonate drilling fluid as following: K+ preventing hydrate expansion, polymer rejection capability, the synergistic effect between the K+ and polymer.Selecting Fang 74-22 and Fang Pu 80-28 as polit areas, and the statistics of thirteen brought–in wells as following: initial daily fluid production rate is 12.9t, initial daily oil production rate is 10.2t, liquid production per unit thickness is 2.5t/(d.m). After three months, initial daily fluid production rate is 9.9t, initial daily oil production rate is 8t, liquid production per unit thickness is 1.6t/(d.m). Through the sulfonate drilling fluid experiments, the drilling fluid systerm which suits Daqing peripheral oil field is selected.