Schlumberger公司的OptiPac机械封隔器可帮助作业者以低廉的成本，实现分层隔离或选择性开采。
编译丨TOM
OptiPac机械封隔器（OSMP）是一种机械激活的静压式裸眼砾石充填封隔器，配有Alternate Path分流管与控制管旁路。当与Alternate Path筛管以及分流管隔离阀（STIV）一起使用时，该封隔器与STIV的组合能够在常规井或大位移井裸眼的不同砾石充填层之间，形成完整的层间隔离。OSMP封隔器可通过各种常用完井方式，实现分层隔离或选择性开采，既可以隔离不需要的层位，也可以封堵未来可能出现的气窜与水侵。
膨胀封隔器需要大约18小时到几天的时间才能膨胀到最大外径，因此需要等待很长时间才能开始进行砾石充填作业。然而，OSMP封隔器在激活后几秒钟内就可形成隔离，从而能够立即执行砾石充填作业。
作业流程
同时下入OSMP封隔器与Alternate Path筛管。每个封隔器都固定在偏心导向芯轴上，使之能够与上下分流管对齐。在同一完井作业中可使用多个封隔器。
当OSMP封隔器、筛管、盲管以及STIV（可选装）下至转盘面以下时，将冲洗管与OSMP封隔器转位工具下入该组合的内部。在第一个封隔器下方30英尺(9米)处，每个OSMP封隔器都对应一个转位工具。转位工具布置在每个后续封隔器下方10英尺（3米）处，以避免发生转位工具面的同时啮合，从而使每个封隔器能够独立坐封。若空间允许，则可以仅利用单个转位工具来激活多个OSMP封隔器。
将OSMP封隔器下入至QUANTUM*砾石充填封隔器或QUANTUM MAX*高温高压封隔器的下方裸眼段中。当OSMP达到目标深度后，对砾石充填封隔器进行坐封与测试。然后上提钻具，使每个冲洗管转位工具都位于对应OSMP封隔器的上方。再下放钻具，使每个坐封滑套与对应的封隔器接合，从而静液柱压力能够使OSMP封隔器实现坐封。由于OSMP封隔器是在泵入砾石之前坐封的，因此所有封隔器的密封件都与井筒接触，确保了完整的层间隔离。
应用
OSMP封隔器的元件设计与Falcon水力压裂裸眼封隔器相同，具有不俗的可靠性，适用于：利用OptiPac* Alternate Path裸眼砾石充填服务的多段裸眼砾石充填井；直井、斜井与水平井；陆地与海上完井作业。
优势
1、可在裸眼完井中创建与隔离层位；
2、可快速坐封，节省作业时间；
3、可实现单井开采多个储层，降低成本；
4、可选择性或智能完井，提高作业效率，增加产量；
5、Alternate Path系统旁路可在封隔器坐封后进行砾石充填；
6、可封堵未来的水侵与气窜。
特点
1、分流管隔离阀，可实现砾石充填层之间的层间隔离；
2、利用冲洗管转位工具进行静液压坐封；
3、PT仪表的控制管旁路；
4、兼容5至5.5寸的Alternate Path裸眼砾石充填筛管与光纤适用的筛管；
5、元件之间的额定压差为3000 psi（21MPa）。
案例分析
道达尔安哥拉石油公司曾计划将位于Kaombo深水开发项目的堆叠沉积层进行混合开采。每口井开采多个油藏层，可减少油井数量，从而减少资本支出。A油田拥有5个产油层，在1井中，由于沥青质沉淀的风险，其中一个储层采出的油与其他储层不相容，无法实现合采。在2井中，含水层位于油层之间。这两口井在开采上、下层时都需要隔离风险层位。
一个或多个储层的水侵会给混合开采带来风险。当最终发生水侵时，必须降低产量以推延事故的发生，并采取昂贵的堵水措施。B油田中的3井拥有四个目标层位，但下部三个层位都面临上述挑战。该井非常需要理想的堵水能力。道达尔公司选择了裸眼砾石充填完井技术，因为多层压裂充填技术的复杂性与成本高得令人望而却步。
一般情况下，Alternate Path筛管与并联的膨胀封隔器可作为多层裸眼砾石充填技术的解决方案。但封隔器膨胀过程太过缓慢，导致钻机处于长时间停机等待状态，特别是对于日费极高的深水作业，显著增加了作业成本。而且，在膨胀完成之前泵入砾石，会导致砾石进入封隔器组件与井筒之间的环空，从而干扰有效的封隔。
新型OSMP OptiPac机械封隔器解决了上述所有烦恼。当坐封工具穿过机械激活式封隔器时，仅需几秒钟的时间，即可实现静液柱坐封。然后就可以立即进行砾石充填，不会影响密封，且节省大量作业时间。该封隔器还配备了经过现场验证的Alternate Path分流管。一旦最上面的区域被填满，砾石将通过分流管转移到下一区域，并且重复该过程，直至所有的区域都被填满。
在1井和3井中，利用OptiPac裸眼砾石充填服务与OSMP封隔器完成了砾石充填作业，并通过井下测量数据与质量平衡分析进行了验证。两个OSMP封隔器封隔了1井不需要的层位，实现了区域隔离，减少了2口井的数量，节约总计超过1亿美元。
3井中的单封隔器可在未来发生水侵时，通过坐封于盲管内的高膨胀率桥塞，封堵下部储层。经济有效的水管理技术使道达尔公司有机会增加产量，提高最终采收率。油藏模拟显示，堵水措施可使B油田增产100万桶原油当量。
2井计划在晚些时候执行裸眼砾石充填完井作业。它将利用两个OSMP封隔器以及夹在它们中间的分流段来隔离水层。道达尔目前正计划将在后续油井中部署更多的OSMP封隔器。
The OSMP* OptiPac service mechanical packer is a mechanically activated hydrostatically set openhole gravel-pack packer with Alternate Path shunt tubes and control line bypasses. When used with Alternate Path screens and the shunt tube isolation valve (STIV), the packer-STIV assembly enables complete zonal isolation between different gravel-packed zones in openhole conventional or extended-reach wells. Zonal isolation or selective production is enabled with the OSMP packer through a variety of common completion architectures either to isolate unwanted zones or for future water and gas shutoff.
Unlike swell packers, which require roughly 18 hours to several days to swell to maximum outside diameter and provide zonal isolation prior to starting the gravel packing, the OSMP packer sets within seconds once activated, enabling gravel packing to commence immediately.
Operating procedure
The OSMP packer is run in conjunction with Alternate Path screens. Each packer is built upon an eccentrically-oriented mandrel, enabling the OSMP packer to be properly aligned with the shunt tubes above and below. Multiple packers can be used within the same sandface completion.
After the OSMP packers, screens, blank pipe, and optional STIVs are run below rotary table, the washpipe and OSMP packer shifting tools are run inside the assembly. One shifting tool is run per OSMP packer placed 30 ft [9 m] below the first packer. The next shifting tool is placed an additional 10 ft [3 m] below each subsequent packer to avoid simultaneous engagement of the shifting tool’s profile, enabling each packer to be set independently. If space-out permits, a single shifting tool can be deployed to set multiple OSMP packers.
The OSMP packer is run into the open hole below a QUANTUM* gravel-pack packer or QUANTUM MAX* HPHT gravel- and frac-pack packer, which is set in the cased hole. Upon reaching the proper depth, the gravel-pack packer is set and tested. Service tool positions are located and—if required—the open hole displaced. The service tool is then picked up, placing each washpipe shifting tool above its corresponding OSMP packer. Subsequently, the workstring is slacked downward, engaging each setting sleeve within the corresponding packer and enabling hydrostatic pressure to set the mechanical OSMP packer. Because OSMP packers are set prior to pumping gravel, all the packer seals are in contact with the wellbore, ensuring complete zonal isolation.
Proven element design
The OSMP packer element is the same design as used in the field-proven Falcon hydraulic-set openhole packer, which has more than 4,000 successful deployments.
APPLICATIONS
Multizone openhole gravel-packed wells that use the OptiPac* Alternate Path? openhole gravel-pack service
Vertical, deviated, and horizontal wells
Land and offshore environments
BENEFITS
Creates and isolates zones in openhole completions
Saves rig time with instantaneous setting
Reduces cost by enabling a single well to access multiple reservoirs
Allows for selective or smart completions for efficient and increased production
Alternate Path system bypass allows gravel packing after packers are set
Enables future water and gas breakthrough shutoff
FEATURES
Shunt tube isolation valve for zonal isolation between gravel-packed zones
Hydrostatically setting with washpipe shifting tool
Control line bypasses for PT gauges
Compatibility with 5- and 5?-in Alternate Path openhole gravel-pack screens and fiber-optic-compatible screens
Differential pressure rating of 3,000 psi [21 MPa] across element
CASE STUDY
Total E&P Angola had planned commingled production from stacked sedimentary layers located in the Kaombo deepwater development. Targeting multiple reservoir layers with each well would reduce well count and therefore capex. Field A consists of five layers; in one instance (Well 1), oil from one of the layers is incompatible with the rest and cannot be commingled because of the risk of asphaltene precipitation. In a second well (Well 2), a water-bearing layer is located between the oil layers. Both wells required isolation of the problematic layers while producing the layers above and below.
Water breakthrough in one or more reservoir layers is a risk associated with commingled production. The rate of production would have to be reduced to delay the event and costly remedial operations undertaken for water shutoff when the breakthrough eventually occurred. This was the challenge presented by the lower three of the four layers targeted by Well 3 in field B. Water shutoff capability was highly desirable in this well. Total’s completion technique of choice was openhole gravel packing because the complexity of multizone frac-pack technology was deemed high risk and the cost was prohibitive.
Alternate Path screens and shunted swell packers have traditionally provided a solution for multizone openhole gravel packing, but the packer swelling process is slow, increasing costs—especially in deepwater applications—while the rig waits. Pumping gravel before swelling is complete can cause the gravel to enter the packer element–wellbore annulus, preventing an effective seal.
The new OSMP OptiPac service mechanical packer addresses all these concerns. The mechanically activated packer is hydrostatically set in a matter of seconds as the setting tool moves through it. Gravel packing can begin immediately without affecting the seal, saving a significant amount of rig time. The packer is equipped with field-proven Alternate Path shunt tubes. Once the uppermost zone is packed, gravel is diverted through the shunt tubes to the next zone, and the process repeats until all the zones are packed.
OptiPac openhole gravel-pack service and OSMP packers delivered complete gravel packs in Wells 1 and 3, confirmed by downhole gauge data and mass balance analysis. Two OSMP packers straddling the unwanted zone in Well 1 and shunted blanks across the zone enabled isolation of the zone, reducing the well count by two and saving Total >USD 100 million.
A single packer in Well 3 provides the ability to seal off the lower reservoir layers by setting a high-expansion plug in a section of blank pipe when water breaks through in the future. Cost-effective water management gives Total the opportunity to produce at an accelerated rate and improves ultimate recovery. Reservoir simulations show that water shutoff can result in an incremental production of 1,000,000 BOE from field B.
Well 2 is scheduled for openhole gravel-pack completion at a later date; it will use two OSMP packers with shunted blanks in between to isolate the water zone. Total is currently evaluating the deployment of additional OSMP packers in future wells.