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Production Diagnostics and Water Control for the XJG Fields, South China Sea

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Production Diagnostics and Water Control for the XJG Fields, South China Sea

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    1. 1 Production Diagnostics and Water Control for the XJG Fields, South China Sea Zhizhuang Jiang, Tao Zhang, ConocoPhillips; Khong Chee Kin, Robert North, Schlumberger Good afternoon, ladies and gentlemen, I’m Jiang Zhizhuang from ConocoPhillips. Together with my colleague Zhang Tao and my Schlumberger friends Mr. Khong Cheekin and Mr. Robert North, we’d like to share with you the topic of Production Diagnostics and water control for the Xijiang fields, South China Sea.Good afternoon, ladies and gentlemen, I’m Jiang Zhizhuang from ConocoPhillips. Together with my colleague Zhang Tao and my Schlumberger friends Mr. Khong Cheekin and Mr. Robert North, we’d like to share with you the topic of Production Diagnostics and water control for the Xijiang fields, South China Sea.

    2. 2 Here is one of our two platforms…Here is one of our two platforms…

    3. 3 XJG Geographic Location And they are located offshore in the South China Sea about 130 km southeast of Hong Kong.And they are located offshore in the South China Sea about 130 km southeast of Hong Kong.

    4. 4 XJG Fields The fields consist of three geological structuresThe fields consist of three geological structures

    5. 5 XJG Geological Characteristics Anticline, Marine Faces delta plain or delta front deposition, multi-stacked reservoirs Most sands are clean, unconsolidated and continuous, oil gravity 26-40 API High porosity(20-33%) and High permeability (Darcy plus range) Large bottom water, strong aquifer support Almost no gas, GOR is around 10 scf/bbl And they are Anticline, Marine Faces delta plain or delta front deposition, multi-stacked reservoirs with high porosity high permeability sands which are clean, unconsolidated and continuous, in a large bottom water aquifer oil gravity ranging 26-40 API , Almost no gas, GOR around 10 scf/bblAnd they are Anticline, Marine Faces delta plain or delta front deposition, multi-stacked reservoirs with high porosity high permeability sands which are clean, unconsolidated and continuous, in a large bottom water aquifer oil gravity ranging 26-40 API , Almost no gas, GOR around 10 scf/bbl

    6. 6 Production Trends As the reservoir pressure has been strongly supported by a bottom water aquifer, it’s only a few psi below the original value after years of production. The good thing is that this has helped to sweep hydrocarbons.... the bad thing is that the high permeability layers have allowed rapid water break-through. Now after 12 years of production the field average water cut has already reached 90% and the total fluid production is close to the processing capacity limit. So water control is big part in our fields. As the reservoir pressure has been strongly supported by a bottom water aquifer, it’s only a few psi below the original value after years of production. The good thing is that this has helped to sweep hydrocarbons.... the bad thing is that the high permeability layers have allowed rapid water break-through. Now after 12 years of production the field average water cut has already reached 90% and the total fluid production is close to the processing capacity limit. So water control is big part in our fields.

    7. 7 Example A Ok, let’s look at our example A,Ok, let’s look at our example A,

    8. 8 Production Logging Challenges High Deviation High Flow Velocity High Water Cut Relatively Heavy Oil This schematic from our example A, illustrates many of the challenges for production logging measurements: The well has 9-5/8” casing, all the way to the bottom. An ESP is suspended on 5-1/2” production tubing with a y-tool and 2-7/8” bypass tubing to allow logging access to the reservoir interval. In the reservoir we have two zones producing: with high-rate water pack completion in one zone and frac-pack in the other. Also, from a previous workover, there are some perforations at the top of the reservoir, which have been abandoned by squeezing cement into the perforations and then insolated them with the tubing and packers. The wellbore deviation in the completion averages about 30 degrees. The high water cut production with relatively heavy oil flows mainly through 3.5” tubing, which results in high flow velocities. This schematic from our example A, illustrates many of the challenges for production logging measurements: The well has 9-5/8” casing, all the way to the bottom. An ESP is suspended on 5-1/2” production tubing with a y-tool and 2-7/8” bypass tubing to allow logging access to the reservoir interval. In the reservoir we have two zones producing: with high-rate water pack completion in one zone and frac-pack in the other. Also, from a previous workover, there are some perforations at the top of the reservoir, which have been abandoned by squeezing cement into the perforations and then insolated them with the tubing and packers. The wellbore deviation in the completion averages about 30 degrees. The high water cut production with relatively heavy oil flows mainly through 3.5” tubing, which results in high flow velocities.

    9. 9 What happened… This well had a great decrease in oil rate, with the same pump under the same working settings, flowing at 9600 bfpd with 94% watercut. So, what happened is that this well had a big drop in oil, with at high fluid rate and high watercutSo, what happened is that this well had a big drop in oil, with at high fluid rate and high watercut

    10. 10 PLT tool string So we decided to run a PLT to see what’s going on downhole And this is the PLT tool string we used So we decided to run a PLT to see what’s going on downhole And this is the PLT tool string we used

    11. 11 A highlight of this tool is the flowmeter and caliper section at the bottom of the string. In addition to spinner and x-y caliper measurements, there are 4 electrical probes deployed on the caliper arms. The electrical probes measure water holdup and bubble counts based on conductivity. These measurements are not affected by deviation or friction effects and they do not require knowledge of downhole fluid properties as required by other holdup tools like capacitance and fluid density. A highlight of this tool is the flowmeter and caliper section at the bottom of the string. In addition to spinner and x-y caliper measurements, there are 4 electrical probes deployed on the caliper arms. The electrical probes measure water holdup and bubble counts based on conductivity. These measurements are not affected by deviation or friction effects and they do not require knowledge of downhole fluid properties as required by other holdup tools like capacitance and fluid density.

    12. 12 Example A - Interpretation And This is the resultant PLT data and interpretation. (Point1: leaking identified) Let’s look at the flowmeter curve first, (1st click) this curve shows that we got three inflows into the wellbore, and this is also confirmed by the temperature curve. BUT, remember the well only got two zones producing, there must be somewhere leaking. (2nd click) See?(3rd click) it’s right here and it’s leaking a lot out of an abandoned zone. Now let’s see is it leaking mainly oil or water? Look at the density curves,(4th click) unfortunately they are not so meaningful, the gradiomanometer must be heavily impacted by the friction effect,. On the other hand, the electrical probes,(5th click) however, are not affected by friction, and therefore the corresponding water holdup clearly indicates that the leaking fluid is mainly water. (Point2: e probe working well in identifying oil entries) How about other zones, (6th click) let’s take a look at the bottom zone,(7th click) the electrical probes easily spotted the first oil entry, while the density has difficulty detecting it. And This is the resultant PLT data and interpretation. (Point1: leaking identified) Let’s look at the flowmeter curve first, (1st click) this curve shows that we got three inflows into the wellbore, and this is also confirmed by the temperature curve. BUT, remember the well only got two zones producing, there must be somewhere leaking. (2nd click) See?(3rd click) it’s right here and it’s leaking a lot out of an abandoned zone. Now let’s see is it leaking mainly oil or water? Look at the density curves,(4th click) unfortunately they are not so meaningful, the gradiomanometer must be heavily impacted by the friction effect,. On the other hand, the electrical probes,(5th click) however, are not affected by friction, and therefore the corresponding water holdup clearly indicates that the leaking fluid is mainly water. (Point2: e probe working well in identifying oil entries) How about other zones, (6th click) let’s take a look at the bottom zone,(7th click) the electrical probes easily spotted the first oil entry, while the density has difficulty detecting it.

    13. 13 Example B Now example BNow example B

    14. 14 This is the well we are talking about, and it’s completed as a commingled, cased hole perforation in 9-5/8” casing.This is the well we are talking about, and it’s completed as a commingled, cased hole perforation in 9-5/8” casing.

    15. 15 Interpretation of 1st PLT When the watercut climbed to 80%, we ran a conventional PLT to see what happened. Here we are looking at the PLT interpretation, see, we got 3 zones dominating the production, where two of them water zones with other being around 60% watercut, but all the rest zones have little opportunity contributing. So in order to shut off water, and let minor zones have better chance to produce, we decided to casing patch these 3 dominating zones.When the watercut climbed to 80%, we ran a conventional PLT to see what happened. Here we are looking at the PLT interpretation, see, we got 3 zones dominating the production, where two of them water zones with other being around 60% watercut, but all the rest zones have little opportunity contributing. So in order to shut off water, and let minor zones have better chance to produce, we decided to casing patch these 3 dominating zones.

    16. 16 and we did so.and we did so.

    17. 17 BUT, after the patching job, the watercut for this well was even higher, Why?? But To our surprise, after the job, the water cut increased to 97% from the pre-job 80%, and we wondered why, so this time we run a 2nd PLT with electrical probes, trying to find out the answerBut To our surprise, after the job, the water cut increased to 97% from the pre-job 80%, and we wondered why, so this time we run a 2nd PLT with electrical probes, trying to find out the answer

    18. 18 Example B – High Water Cut Zone Here’s the PLT result. As we can see, The 3 casing patch positions from the prior workover are clearly shown on the caliper data. And most of the water inflow in this well is from X600 meters, an interval which was previously patched! So the answer is: the top patch failed to work, and there’s a big leak from it, dominating the well bore at 86% of the total fluid and, it’s water! Here’s the PLT result. As we can see, The 3 casing patch positions from the prior workover are clearly shown on the caliper data. And most of the water inflow in this well is from X600 meters, an interval which was previously patched! So the answer is: the top patch failed to work, and there’s a big leak from it, dominating the well bore at 86% of the total fluid and, it’s water!

    19. 19 Based on the X-Y caliper response, let’s take a closer look at the curves, the green bars are the planned perforations, while the red ones show the actual perforations. So the data is telling us that the perforations are systematically 3 meters deeper than planned. So this could explain the leaking patch in the upper zone, it also helps explain the poor performance from the smaller zones. Wow, another surprise!Based on the X-Y caliper response, let’s take a closer look at the curves, the green bars are the planned perforations, while the red ones show the actual perforations. So the data is telling us that the perforations are systematically 3 meters deeper than planned. So this could explain the leaking patch in the upper zone, it also helps explain the poor performance from the smaller zones. Wow, another surprise!

    20. 20 According to PLT results above, we straddled off the leaking zone, and re-perforated the smaller zones. According to PLT results above, we straddled off the leaking zone, and re-perforated the smaller zones.

    21. 21 As a result, the production was gained by an extra of 2000 bopd, the watercut was reduced to around 70% As a result, the production was gained by an extra of 2000 bopd, the watercut was reduced to around 70%

    22. 22 Example E Example EExample E

    23. 23 This is a brand-new sidetrack well, completed as a commingled, cased hole perforation in 7-in. casing. This is a brand-new sidetrack well, completed as a commingled, cased hole perforation in 7-in. casing.

    24. 24 The open hole log shows that the oil saturation is good. See for the major zones the oil saturation is 60 to 80%, and that is to say, the water saturation is only 20% to 40%The open hole log shows that the oil saturation is good. See for the major zones the oil saturation is 60 to 80%, and that is to say, the water saturation is only 20% to 40%

    25. 25 HOWEVER, The initial production showed a watercut, disappointingly high as 70% WHY??? However, the initial production shows a very high watercut, and this result totally disagrees with the OH log, so we wonder why?However, the initial production shows a very high watercut, and this result totally disagrees with the OH log, so we wonder why?

    26. 26 Example E – PLT interpretation The subsequent production logging showed the fourth zone from top contributes most of the fluid at 50% water cut, while the top two perforations flowed almost entirely oil. and the results are in agreement with the OH oil saturation analysis. but why the surface watercut is still so high? The subsequent production logging showed the fourth zone from top contributes most of the fluid at 50% water cut, while the top two perforations flowed almost entirely oil. and the results are in agreement with the OH oil saturation analysis. but why the surface watercut is still so high?

    27. 27 Here’s why… Based on the PLT result, the integrity of the casing was tested and a leak around 700m above the completion interval was found responsible for the increased watercut. So based on the PLT observations, later on, Drilling conducted a casing integrity test, A leak was found from the 9-5/8” casing 700 m above the logging interval and it’s responsible for the high surface water cut. So based on the PLT observations, later on, Drilling conducted a casing integrity test, A leak was found from the 9-5/8” casing 700 m above the logging interval and it’s responsible for the high surface water cut.

    28. 28 CONCLUSIONS Production Logging plays an important role in production optimization in XJG field. Electrical Probe Sensors overcome the limitations of conventional fluid density and capacitance sensors Through Tubing Caliper data is very useful to help verify perforation depth and completions By the way, there are several other examples available in the paper but not shown here due to time constraints. So, let’s go to conclusions… PLT is important in the production diagnostics and production optimization in XJ fieldBy the way, there are several other examples available in the paper but not shown here due to time constraints. So, let’s go to conclusions… PLT is important in the production diagnostics and production optimization in XJ field

    29. 29 Acknowledgement Thank the management of CNOOC, ConocoPhillips, Shell, and Schlumberger for their support and permission to publish this paper. Special thanks to Mr. Tuan Ma, Mr. Liu Congyin for their help in this paper In the acknowledgement, we’d like to … We would also like to express special thanks to Mr. Tuan Ma from ConocoPhillips and Mr. Liu Congyin from CNOOC for their help in this paper.In the acknowledgement, we’d like to … We would also like to express special thanks to Mr. Tuan Ma from ConocoPhillips and Mr. Liu Congyin from CNOOC for their help in this paper.

    30. 30 Thank you! Questions, please?

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