Underground mud communication transmission method

Abstract

An underground slurry communication transmission method belongs to the technical field of petroleum drilling engineering, adopts a cyclic PN sequence for information transmission, and comprises the following steps: 1) generating a group of cyclic PN sequences; (2) at a transmitting end, signals collected underground are mapped to a cyclic PN sequence through a mapping rule, an underground valve is controlled through the cyclic PN sequence to generate pulses, and the pulses are transmitted through a mud medium; and 3) at a receiving end, constructing a cyclic PN sequence receiving system, performing synchronization through a detection means in a matrix form to obtain synchronous bias, performing cyclic correlation operation on a signal and the converted cyclic PN sequence, and resolving information sent by a transmitting end. According to the invention, the cyclic PN sequence is adopted to replace the traditional Marry coding, the defect of low information rate of the traditional coding mode is overcome, and the cyclic PN code can effectively reduce the error rate in the signal transmission process; in the synchronization process, a detection means in a matrix form is adopted, the synchronization accuracy is improved, and it is ensured that underground signals can be accurately and efficiently transmitted back to the ground.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil drilling engineering and relates to a downhole mud communication transmission method. BACKGROUND

[0002] In the process of oil drilling, the measurement-while-drilling technology is used to obtain downhole formation parameters, and information transmission between the downhole and the ground is realized by generating pulse signals through the opening and closing of downhole valves. It is proposed in the document Che Weijin, Li Jin. Measurement information coding and decoding technology of MWD and LWD drilling instruments [J]. Science and Technology, 2012, (16): 14. DOI:10.19392 / j.cnki.1671-7341.2012.16.006. that the coding mode of pulse position coding, Manchester coding and optimized combination code is used. However, these coding modes have defects, and the information rate is slow, which is difficult to meet the needs of modern oil drilling for real-time and efficient transmission of downhole information.

[0003] Therefore, there is an urgent need for a communication transmission mode that can improve the information transmission rate and high reliability. SUMMARY

[0004] In view of the problems of slow information transmission rate and low reliability in the prior art, the application provides a method for improving the reliability and effectiveness of downhole signal return to the ground.

[0005] In order to achieve the above purpose, the technical scheme adopted by the application is:

[0006] A downhole mud communication transmission method, which uses a cyclic PN sequence for information transmission. The first part: a set of cyclic PN sequences is generated in advance; the second part: at the transmitting end, the signals collected downhole are mapped to the cyclic PN sequence through a mapping rule, and the cyclic PN sequence is used to control the downhole valve to generate a pulse, and the pulse is transmitted through the mud medium; the third part: at the receiving end, a cyclic PN sequence receiving system is constructed, synchronization is performed through a matrix form detection means, a synchronization bias is obtained, and then the signal and the converted cyclic PN sequence are cyclically correlated starting from the synchronization element, and the information sent by the transmitting end is solved.

[0007] Specifically, the following steps are included:

[0008] Step one: generate a set of cyclic PN sequences;

[0009] Step 1.1, generate a family of PN sequence base codes p i =[p i,1 ,p i,2 ,…,p i,L ],1≤i≤N, where each element p i,a ∈{1,-1},a∈{1,2,...,L}.

[0010] Step 1.2, the PN sequence base code is right cyclically shifted k bits, and the obtained form is That is, the cyclic PN sequence.

[0011] Step 1.3, the transmitted information is represented as where i∈{1,2,…,N},1≤k≤L,s∈{-1,+1},i represents the ID of the sequence corresponding to the base code, k represents the displacement of the sequence relative to the base code, and s represents the positive and negative of the sequence.

[0012] At the transmitting end, after the downhole sensor receives external information, the information is mapped into a cyclic PN sequence through a mapping rule, and then sent out in the form of a pulse through the mud pump valve, and the specific steps are as follows:

[0013] Step two: after the sensor in the device collects information, the information is mapped with the cyclic PN sequence through a mapping rule (for example, the information received by the sensor is converted into several binaries, and the several binaries are represented by a cyclic PN sequence). Form a sequence A composed of several cyclic PN sequences.

[0014] Step three: according to the cyclic PN sequence in A p i,k ,p i,k+1 ,…,p i,L ,p i,1 ,p i,2 ,…,p i,k-1 control the opening and closing timing of the downhole mud pump valve to generate corresponding pulse signals. (For example, the value of p i,k is "1", which corresponds to the valve closing to generate a positive pulse, and "-1" corresponds to the valve opening without pulse, or vice versa. Assuming that the length of the pulse is T, the length of a cyclic PN sequence is TL)

[0015] At the receiving end, a cyclic PN sequence receiving system is constructed to receive the signal sent by the transmitting end, synchronize through a matrix form detection means, and then solve the data through correlation operation. The specific method is as follows:

[0016] Step four: a group of signals R is received at the receiving end, assuming that its length is (W+1)TL,W∈{1,2,3,4,5,6...}, the sampling frequency of the receiving end is H, and R is composed of (W+1)THL sampling points. The end of the signal R received first is called the front end, and the end received last is called the rear end. Set a threshold t to binarize the signal R to obtain R * ∈{1,-1}, R * is composed of (W+1)THL elements, and R *The front end of p corresponds to the front end of R, R * The back end of p corresponds to the back end of R. The cyclic PN sequence base code p i = [p i,1 , p i,2 ,..., p i,L ], 1≤i≤N is repeated TH times to obtain p * i = [p i,1 , p i,1 ,..., p i,1 , p i,2 , p i,2 ,..., p i,2 ,..., p i,L , p i,L ,..., p i,L ], 1≤i≤N, p * i is composed of THL elements. The first element in p * i is aligned with the first element at the front end of R * , the second element in p * i is aligned with the second element at the front end of R * , and so on. The elements in p * i that are shifted relative to R * are recorded, and S is initialized to 0.

[0017] Step five: the detection means in the form of a matrix is synchronized;

[0018] Step 5.1: cyclic correlation operation is performed on the part of p * i that is currently aligned with R * , to obtain N cyclic correlation functions, denoted as wherein C N (τ) represents a correlation function obtained by performing cyclic correlation operation on the part of p * N that is aligned with R * ;

[0019] Step 5.2: the absolute value of is taken, and the maximum peak value is found and denoted as

[0020] Step 5.3: p * i is aligned after being shifted by one element relative to R * , and the direction of the shift is from the front end to the back end, S=S+1;

[0021] Step 5.4: judge whether S is greater than THL-1, if yes, execute step 5.5; otherwise, repeat step 5.1, 5.2, 5.3;

[0022] When S is greater than THL-1, THL maximum peaks have been obtained, which are composed of a peak array, denoted as Wherein represents p * i The first time relative to R * Shift THL-1 elements to calculate the maximum peak. Form a shape similar to a triangle.

[0023] Step 5.5: initialize S to 0, repeat step 5.1, 5.2, 5.3, 5.4 until p * i Traverse each element in R * .

[0024] p * i Traverse each element in R * , obtain W peak arrays, denoted as Write it in the form of matrix as follows:

[0025]

[0026] Wherein, represents p * i The Wth time relative to R * Shift THL-1 elements to calculate the maximum peak

[0027] Step 5.6: combine formula (1) by column to obtain:

[0028]

[0029] The maximum value in m sum is θ is the offset of the starting element in R * to the synchronization element, and the synchronization is completed.

[0030] Step six: solve the data by circular correlation operation:

[0031] Step 6.1: intercept the first to the THLth element of R * from the synchronization element as the starting point, denoted as B (1) .

[0032] Step 6.2: p * i and B(1) Align and perform cyclic correlation operation to obtain N cyclic correlation functions, denoted as

[0033] Step 6.3: select The absolute value of the peak value of the maximum correlation function

[0034] Step 6.4: according to the peak value in The offset k1 is obtained in the position interval of , and s1 is obtained by the positive and negative of the peak value, and

[0035] Step 6.5: according to the mapping rule mentioned in step two, D1 is converted into information.

[0036] Step 6.6: R * The THL+1 to the 2THL element at the back end is intercepted from the synchronization element as the starting point, denoted as B (2) , and so on.

[0037] Step 6.7: repeat steps 6.1 to 6.6 until all elements in R * are traversed.

[0038] The effects and benefits of the present application are:

[0039] (1) The present application uses cyclic PN sequence instead of traditional Marry coding, which overcomes the slow information rate of traditional coding method, and the cyclic PN code has the characteristics of high reliability, which can effectively reduce the bit error rate in the signal transmission process.

[0040] (2) In the synchronization process, the detection means in the form of matrix is adopted, which improves the accuracy of synchronization and ensures that the downhole signal can be accurately and efficiently returned to the ground. DETAILED DESCRIPTION

[0041] The specific embodiments of the present application will be described in detail below in combination with the technical solutions.

[0042] A method for downhole mud communication transmission, the specific steps are as follows:

[0043] Step one: generate a group of cyclic PN sequences with length 7 and number 9;

[0044] Step 1.1, generate a family of PN sequence base codes p i =[p i,1 ,p i,2 ,…,p i,L ], 1≤i≤9, L=7, wherein each element p i,a ∈{1,-1}, a∈{0,1,...,L}.

[0045] Step 1.2: Circularly shift the PN sequence base code to the right by k bits to obtain the following form: This is a cyclic PN sequence.

[0046] Step 1.3, will The transmitted information is represented as Where i∈{1,2,…,9},1≤k≤L,s∈{-1,+1}, i represents the ID of the base code corresponding to the sequence, k represents the shift of the sequence relative to the base code, and s represents the sign of the sequence.

[0047] At the transmitting end, the downhole sensor receives information and maps it into a cyclic PN sequence. The cyclic PN sequence is then transmitted to the receiving end via the mud medium. The specific steps are as follows:

[0048] Step 2: Downhole, after the sensors in the equipment collect information, the information is mapped to a cyclic PN sequence using a mapping rule (for example, the information received by the sensor is converted into several binary numbers, and these binary numbers are represented by a cyclic PN sequence). This forms a sequence A consisting of several cyclic PN sequences.

[0049] Step 3: Based on the cyclic PN sequence in A p in i,k ,p i,k+1 ,…,p i,L ,p i,1 ,p i,2 ,…,p i,k-1 The opening and closing sequence of the downhole mud pump valves is controlled to generate corresponding pulse signals. (For example, p) i,k A value of "1" corresponds to a positive pulse when the valve is closed, and "-1" corresponds to no pulse when the valve is open, or vice versa. Assuming the pulse duration is 1 second, the duration of one cyclic PN sequence is 7 seconds.

[0050] At the receiving end, a cyclic PN sequence receiving system is constructed to receive the signal transmitted from the transmitting end. Synchronization is achieved through matrix-based detection, and the data is then processed through relevant operations. The specific method is as follows:

[0051] Step 4: Receive a signal R at the receiving end, assuming its duration is 77 seconds, the sampling frequency at the receiving end is 512 Hz, and R consists of 39424 sampling points. The end of signal R received first is called the front end, and the end received later is called the back end. Set a threshold t to binarize signal R, obtaining Ri. * ∈{1,-1}, R * R consists of 39,424 elements. * The front end corresponds to the front end of R, R *The back end corresponds to the back end of R. The cyclic PN sequence base code p... i =[p i,1 ,p i,2 ,…,p i,L p is obtained by repeating each element in the sequence 1≤i≤9 512 times. * i =[p i,1 ,p i,1 ,...,p i,1 ,p i,2 ,p i,2 ,…,p i,2 ,...,p i,L ,p i,L ,...,p i,L ], 1≤i≤9,p * i It consists of 3584 elements. (The last part, "p", appears to be a typo and can be left as is.) * i The first element in R * Align the first element in the front end, p * i The second element in R * The second element at the front is aligned, and so on. Record p * i Relative to R * The number of elements to be shifted is denoted as S, and S is initialized to 0.

[0052] Step 5: Synchronize using matrix-based detection methods;

[0053] Step 5.1: Put p * i With R * The currently aligned portion undergoes loop dependency operations, resulting in 9 loop dependency functions, denoted as...

[0054] Step 5.2: [The sentence is incomplete and requires more context to be translated accurately.] After taking the absolute value, find the maximum peak value and record it as .

[0055] Step 5.3: p * i Relative to R * After shifting one element, the alignment is performed, with the shift direction from the front end to the back end, S = S + 1;

[0056] Step 5.4: Determine if S is greater than 3583. If it is, proceed to step 5.5; otherwise, repeat steps 5.1, 5.2, and 5.3.

[0057] When S is greater than 3583, 3584 maximum peak values ​​have been obtained. These are grouped into a peak array, denoted as . It forms a shape similar to a triangle.

[0058] Step 5.5: Initialize S to 0, and repeat steps 5.1, 5.2, 5.3, and 5.4 until p. * i After traversing R * Each element in it.

[0059] p * i After traversing R * After each element in the array, we obtain 10 peak arrays, denoted as... It can be written in matrix form as follows:

[0060]

[0061] Step 5.6: Merge formula (1) by column to get:

[0062]

[0063] Then m sum The maximum value in is θ is R * The offset from the starting element to the synchronized element is used to complete synchronization.

[0064] Step Six: Solve the data through iterative related operations:

[0065] Step 6.1: Transfer R * Starting from the synchronized element, extract the first to the 3584th element from the backend, denoted as B. (1) .

[0066] Step 6.2: Put p * i one by one with B (1) Align and perform loop-related operations to obtain N loop-related functions, denoted as...

[0067] Step 6.3: Select Maximum absolute value of mid-peak correlation function

[0068] Step 6.4: According to The peak value in The bias k1 is obtained from the midpoint interval, and s1 is obtained from the sign of the peak value. The result is then obtained from the reconstructed value.

[0069] Step 6.5: According to the mapping rules in Step 2, convert D1 into information.

[0070] Step 6.6: Transfer R* Take the first 3585 to the 7168 elements from the back end of the synchronization element, denoted as B (2) And so on.

[0071] Step 6.7: Repeat steps 6.1 to 6.6 until all elements in R * Middle are traversed.

[0072] The above-described embodiments only express the implementation of the present application, but cannot be understood as limiting the scope of the present application. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application.

Claims

1. A method for downhole mud communication transmission, characterized in that, The method employs a cyclic PN sequence for information transmission. The first part involves pre-generating a set of cyclic PN sequences. The second part involves mapping the downhole collected signals to the cyclic PN sequences using mapping rules at the transmitting end, controlling downhole valves to generate pulses via the cyclic PN sequences, and transmitting the pulses through the mud medium. The third part involves constructing a cyclic PN sequence receiving system at the receiving end, synchronizing using matrix-based detection to obtain a synchronization bias, and then performing cyclic correlation operations between the signal and the converted cyclic PN sequences, starting from the synchronization element, to calculate the information sent by the transmitting end.

2. The method for downhole mud communication transmission according to claim 1, characterized in that, The method specifically includes the following steps: Step 1: Generate a set of cyclic PN sequences; At the transmitting end, after the downhole sensor receives external information, it maps the information into a cyclic PN sequence according to a mapping rule, and then sends it out in the form of pulses through the mud pump valve. The specific steps are as follows: Step 2: Downhole, after the sensors in the equipment collect information, they map the information to a cyclic PN sequence using mapping rules, forming a sequence A composed of several cyclic PN sequences; Step 3: Based on the cyclic PN sequence in A p in i,k ,p i,k+1 ,…,p i,L ,p i,1 ,p i,2 ,…,p i,k-1 The opening and closing sequence of the downhole mud pump valves is controlled to generate corresponding pulse signals; At the receiving end, a cyclic PN sequence receiving system is constructed to receive the signal transmitted from the transmitting end. Synchronization is achieved through matrix-based detection, and the data is then processed through relevant operations. The specific method is as follows: Step 4: Receive a set of signals R at the receiving end. Assume that its duration is (W+1)TL, W∈{1,2,3,4,5,6...}, the sampling frequency at the receiving end is H, and R consists of (W+1)THL sampling points. The end of signal R that is received first is called the front end, and the end that is received later is called the back end. Set a threshold t to binarize the signal R, and obtain Rt * ∈{1,-1}, R * It consists of (W+1)THL elements, R * The front end corresponds to the front end of R, R * The backend corresponds to the R backend; The cyclic PN sequence base code p i =[p i,1 ,p i,2 ,…,p i,L Each element in 1≤i≤N is repeated TH times to obtain p. * i =[p i,1 ,p i,1 ,...,p i,1 ,p i,2 ,p i,2 ,…,p i,2 ,...,p i,L ,p i,L ,...,p i,L ], 1≤i≤N,p * i It consists of THL elements; p * i The first element in R * Align the first element in the front end, p * i The second element in R * The second element at the front is aligned, and so on; record p. * i Relative to R * The number of elements to be shifted is denoted as S, and S is initialized to 0. Step 5: Synchronize using matrix-based detection methods; Step 6: Solve the data through iterative related operations.

3. The method for downhole mud communication transmission according to claim 2, characterized in that, Step one specifically involves: Step 1.1: Generate a family of PN sequence base codes p i =[p i,1 ,p i,2 ,…,p i,L ], 1≤i≤N, where each element p i,a ∈{1,-1}, a∈{1,2,...,L}; Step 1.2: Circularly shift the PN sequence base code to the right by k bits to obtain the following form: This is a cyclic PN sequence; Step 1.3, will The transmitted information is represented as Where i∈{1,2,…,N},1≤k≤L,s∈{-1,+1}, i represents the ID of the base code corresponding to the sequence, k represents the shift of the sequence relative to the base code, and s represents the sign of the sequence.

4. The method for downhole mud communication transmission according to claim 2, characterized in that, In step three, if p i,k A value of "1" corresponds to the valve being closed and generating a positive pulse, while "-1" corresponds to the valve being open and generating no pulse, or vice versa; let the pulse duration be T, so the duration of a cyclic PN sequence is TL.

5. A method for downhole mud communication transmission according to claim 2, characterized in that, Step five specifically refers to: Step 5.1: Put p * i With R * Perform loop dependency operations on the currently aligned portion to obtain N loop dependency functions, denoted as... Among them, C N (τ) represents p * N With R * The correlation function is obtained by performing a cyclic correlation operation on the aligned portion; Step 5.2: [The sentence is incomplete and requires more context to be translated accurately.] After taking the absolute value, find the maximum peak value and denot it as . Step 5.3: p * i Relative to R * After shifting one element, the alignment is performed, with the shift direction from the front end to the back end, S = S + 1; Step 5.4: Determine if S is greater than THL-1. If it is, proceed to step 5.5; otherwise, repeat steps 5.1, 5.2, and 5.

3. When S is greater than THL-1, THL maximum peak values ​​have been obtained. These peak values ​​are grouped into a peak array, denoted as . in p * i The first time relative to R * The maximum peak value calculated after shifting THL-1 elements; It forms a shape similar to a triangle; Step 5.5: Initialize S to 0, and repeat steps 5.1, 5.2, 5.3, and 5.4 until p. * i After traversing R * Each element in; p * i After traversing R * After each element in the array, we obtain W peak arrays, denoted as . It can be written in matrix form as follows: in, p represents * i The Wth time relative to R * The maximum peak value calculated after shifting by THL-1 elements Step 5.6: Merge formula (1) by column to get: Then m sum The maximum value in is θ is R * The offset from the starting element to the synchronized element is used to complete synchronization.

6. The method for downhole mud communication transmission according to claim 5, characterized in that, Step six specifically refers to: Step 6.1: Transfer R * Starting from the synchronized element, extract the first to the THLth elements from the backend, denoted as B. (1) ; Step 6.2: Put p * i one by one with B (1) Align and perform loop-related operations to obtain N loop-related functions, denoted as... Step 6.3: Select Maximum absolute value of mid-peak correlation function Step 6.4: According to The peak value in The bias k1 is obtained from the midpoint interval, and s1 is obtained from the sign of the peak value. The result is then obtained from the reconstructed value. Step 6.5: According to the mapping rules mentioned in Step 2, convert D1 into information; Step 6.6: Transfer R * Starting from the sync element, extract the (+1)th to the 2nd THL element from the backend, denoted as B. (2) And so on; Step 6.7: Repeat steps 6.1 to 6.6 until R has been traversed. * All elements in it.

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