海洋深水高温高压气井环空带压管理

中国南海高温高压油气藏开发过程中,井筒环空带压问题突出,一旦超过允许值将会影响安全生产。为了保证气井的正常生产,需要确定环空压力的合理范围,为此基于ISO 16530-1:2017标准和API RP 90-2的推荐做法,研究并建立了考虑管柱承压能力和关键节点校核的深水高温高压气井环空带压控制值计算模型以及一套环空压力管理图版。研究结果表明:(1)管柱承压能力计算主要针对环空对应的油管和套管;(2)关键节点校核计算主要针对井口装置、封隔器、井下安全阀和尾管悬挂器等;(3)建立了环空最小预留压力计算模型,以确保对深水高地层压力或井底高流压气井的环空施加一定的备压,保证井下管柱和工具在合理环空压力范围内正常工作;(4)以某深水气井为实例进行了计算与分析,得到了考虑和不考虑壁厚减薄情况下随投产时间变化的各环空带压控制值。结论认为,所建立的模型及图版应用于海上深水高温高压气井,使用简便、可操作性强,可以为深水高温高压气井及类似井的井筒环空压力管理提供借鉴。     

深水油气井环空带压预防弹性隔离液体系

深水油气开发过程中,套管圈闭环空内流体温度升高会引起环空带压的现象,严重时会挤毁或胀裂套管,给生产作业带来严重的安全隐患。为解决这一问题,室内研究了一套预防环空带压的弹性隔离液体系,并采用自制的"高温高压弹性流体评价仪"和"弹性材料往复压缩试验仪"对隔离液的性能进行评价。研发的弹性隔离液体系配方为:海水+0.4%悬浮剂HX+6%弹性剂+超细铁矿粉,密度在1.10~1.90 g/cm3内可调。评价结果表明:①该弹性隔离液体系具有高弹性、抗压缩性强的特点,弹性恢复率为100%;②在不同温度条件下能够稳定地保持弹性,缓解压力效果稳定;③与钻井液和水泥浆配伍性较好,不影响弹性隔离液和固井水泥浆施工作业。研发的弹性隔离液体系应用在深水油气井可以缓解和控制环空带压现象。      

FLAT-PRO深水恒流变合成基钻井液及其应用

深水钻井面临低温、安全密度窗口窄、浅层气易形成气体水合物、井壁易失稳等技术难题,对深水钻井液提出了更高的要求。以Saraline 185V气制油为基油,通过优选乳化剂、有机土、降滤失剂及其他处理剂,构建了一套适合深水钻井的FLAT-PRO深水恒流变合成基钻井液体系。综合性能评价结果表明:该钻井液在4~65℃下流变性能稳定,具有恒流变特性,能有效保护储层,其渗透率恢复值大于90%,能抗10%海水、15%钻屑污染,易降解,满足环保要求。南海LS-A超深水井水深为1 699.3 m,预测主要目的层温度为34.6~36℃,φ508 mm套管鞋处的地层承压能力系数低于1.14,安全密度窗口窄,如何控制ECD值、预防井漏是该井的作业控点,因此选择密度为1.03 g/cm3的FLAT-PRO钻井液开钻。钻进过程中,使用FSVIS调整流变性,维护黏度在50~70 s,动切力在8~15 Pa,φ₆读数为7~15,φ₃读数为6~12,用2% PF-HFR控制滤失量,应用井段起下钻顺利,电测顺利,井径规则,没有出现任何复杂情况。应用结果表明,FALT-PRO深水恒流变合成基钻井液在不同温度下的流变性能稳定,抑制性好,润滑性强,能获得较低的ECD值,满足深水钻井的要求。      

一种深水用白油基恒流变钻井液体系的建立与评价

主要针对深海钻井作业设计了一种白油基恒流变钻井液。我们主要通过添加有机土和高分子聚合物来达到钻井液恒流变的目的。还评价了有机土的种类与含量、高分子聚合物的含量、油水比和钻井液密度对白油基钻井液流变性(动切力YP)的影响。     

An intelligent optimization–based prediction model for natural gas hydrate formation in a deepwater pipeline

Temperature, pressure, and composition of gas mixtures in deepwater pipelines promote rapid formation of gas hydrates. To avert this dilemma, it is more significant to find out the temperature and pressure limits in gas hydrates formation of the deepwater pipeline. The objective of this research is to develop an optimization method that finds the optimal temperature and pressure profile for natural gas hydrate formation conditions and an error calculation method to find the realistic approach of the hydrate formation prediction model. A newly developed correlation model is computing the hydrate formation pressure and temperature for a single component of methane (CH₄) gas. The proposed developed prediction model is based on the 2 and 15 constant coefficients and holds a wide range of temperature and pressure data about 2.64 to 46°C and 0.051 to 400 MPa for pure water and methane, respectively. The reducing error discrepancies are 1.2871, 0.35012, and 1.9052, which is assessed by GA, PSO, and GWO algorithms, respectively. The results show the newly developed optimization algorithms are in admirable compliance with the experimental data and standards of empirical models. These correlations are providing the capability to predict gas hydrate forming conditions for a wide range of hydrate formation data.     

深水钻井液添加剂抑制气体水合物生成实验

深水钻井中,水合物的大量生成与聚集是引起防喷器堵塞等事故的直接原因。利用水合物模拟实验装置,模拟了深水钻井动态环境,对深水水基钻井液常用添加剂进行了水合物生成实验研究。以水合物开始大量生成的时间为评价标准,分析了常用加量下深水钻井液添加剂抑制水合物生成效果。结果表明,聚合醇SD-301可显著推迟水合物大量生成的时间,其抑制效果优于常用水合物动力学抑制剂PVCap;聚阴离子纤维素PAC-LV、生物聚合物XC、羧甲基纤维素CMC-LV以及动力学抑制剂PVP也具备一定的抑制效果;而部分水解聚丙烯酰胺PLUS、氨基聚合物SDJA以及磺化酚醛树脂SD-102的抑制效果并不明显。     

What role does stratification play during winter in wind-induced exchange between the multi-depth basins of a large lake (Lake Geneva)?

Detailed studies of wind-driven interbasin exchange in lakes, focusing on the underlying driving forces and how they are affected by stratification, are presently lacking. We therefore investigated how stratification modifies wind-induced exchange between the Petit Lac (PL) (depth 75 m) and Grand Lac (GL) (depth 309 m) basins of Lake Geneva in winter, using field observations, 3D hydrodynamic modeling and particle tracking. Early, weakly-stratified (December) and late, fully-mixed (March) winter conditions in the PL were compared for a typical, strong along-axis wind forcing. During early winter, two-layer exchange develops between the basins, with downwind surface outflow into the GL balanced by intense bottom inflow of deep, cold hypolimnetic GL water into the PL which is enhanced by baroclinic pressure gradients caused by upwelling in the GL. Furthermore, the transversal water-level setup generates barotropic pressure gradients that balance Coriolis force acting on the outflow. This produces unidirectional along-wind epilimnion currents that strengthen interbasin exchange. In late winter, with the thermocline deeper than the PL bottom, upwelling in the GL does not reach the confluence and baroclinicity plays no role, resulting in weaker exchange currents with a depth-veering structure in the upper layers due to Coriolis force. In late winter, interbasin exchange decreases by 50 %, is more local, affects only waters near the confluence, and is more horizontal, with no deepwater upwelling from the GL. Our results suggest that prolonged winter stratification due to global warming will make wind-induced hypolimnetic interbasin-upwelling an increasingly important deepwater renewal process in large multi-depth basin lakes.