Study On Managed Pressure Drilling Technology With Gel Valve For NP Deep High Temperature Buried Hill

The NP buried hill reservoir is characterized by complex geological conditions,deep burial reservoir,high temperature(138-185.2?),development of fractured holes and high ratio of gas to oil,etc.The drilling safety density has a narrow window,and well leakage,overflow and other frequently happening downholes during drilling.This study proposes the technical ideas using the MPD technology to solve the well leakage and overflow of the NP high temperature buried hill reservoir narrow safety density window stratum,combined with the gel valve technology.The thesis has achieved the following main research results:(1)Developed a high-temperature resistant gel system with the optimal formula:0.3%JH-108+0.25%double-stage cross-linking agent+0.13%acid-base conditioner+0.15%oxygen scavenger,and the gel system has twice gelation characteristics,after the gel viscosity reached 65000mPa·s,its temperature index reached 180?,much higher than domestic and foreign similar products(120?),enable meet the temperature resistance of NP high temperature buried hill reservoir to gel valve system demanding.(2)The high-temperature wellbore visualization experimental device of the gel valve was developed.Through the experimental and numerical simulation studies,it was found that due to the injection of the drill pipet caused the difficulty of "reunion" and the phenomenon of"mixed slurry",the certainly length of gel segment is invalid.;the gel segment has a higher static pressure capacity,the gas intrusion will reduce the colloidal strength;the pressure bearing capacity of the gel is related to the operation process,if the well leakage or gas invasion occurs when the gel is injected,it will cause the effective of the gel.The reduction in the length of the section reduces its pressure bearing capacity.If there is a hole leakage or gas intrusion after the gel completed,the pressure bearing capacity is not changed.The vertical wellbore gel has the largest pressure bearing capacity.With the increase of the well angle,the pressure bearing capacity is significantly reduced.Erosion breakers and gel breakers can all complete the broken gel.The gel breaker breaks the gel more thoroughly,but the gel breakage time is slightly longer.(3)The laboratory experiment about vertical wellbore and horizontal wellbore for the fractured formations that blow out-lost circulation coexistence.The results showed that the leakage rate,gas overflow,bottomhole pressure difference,fracture width,and viscosity were related.bottomhole pressure balance condition will not changed the blow out-lost circulation coexistence phenomenon,but it will have a great influence on the blow out-lost circulation coexistence strength.Based on experimentally obtained frame-type laws,The leakage spray function that a blow out-lost circulation coexistence for narrow safety density window is established.Combined with the on-site Drill Leakage Test,it theoretically yields quantified results that are meaningful to the specific formation.(4)Conducted the MPD of a gel valve research that associated with hydrodynamics studies,a single-phase flow model for the wellbore drilling fluid,a pressure fluctuation model for the hoisting and feeding-off,a wellbore pressure fluctuation model for the on-off pump,and a two-phase flow transient in the air-liquid two-phase flow were established.Based on the flow model,constructed a fluid dynamics model system for the MPD of a gel valve.Based on the established model,the transient flow and pressure evolution laws of the wellbore during normal circulation,the hoisting and feeding-off,switch pump and gas invasion were studied.(5)Established the gel valve determination method of key process parameters such as depth of entry,slug length,pumping volume of the gel valve and pump pressure,etc.,and studied the main influencing factors of various process parameters based on numerical calculations.The theoretical calculation chart of the gel slug length,the pumping amount and the injecting pump pressure under different parameters.(6)Established the operating procedures for the gel valve normal drilling,drilling a narrow safe density window,drilling through a narrow safe density window,and ending the drilling process,etc,and for the development of the high temperature resistant gel.The system successfully conducted field tests in drilling and completion operations after the MPD at the NP23-P2016 well and well repair operations at the Baogu-2 well.In the two well operations had not occurred well leakage and overflow,and effective protection was achieved.In the reservoir,the production of the two wells was higher than that of the neighboring wells or before the construction,demonstrating the unique technical advantages of the high temperature resistant gel system in the pressure control of the wellbore and the protection of the reservoirs.The MPD technology of the gel value overcomes the engineering porblems successfuly such as leakage and frequent overflow during the drilling of the NP deep high-pressure buried hill narrow safe density reservoir,protecting the reservoir effectively,which is contributed to the efficient exploration and development of NP deep buried hill reservoir.At the same time,the proposal of this technology also provides feasible technical options for solving the problem of blow out-lost circulation coexistence of drilling wells in a narrow safety density window in China.